diff --git a/src/models/entities/Address.ts b/src/models/entities/Address.ts
index 6cc1d11..54c490e 100644
--- a/src/models/entities/Address.ts
+++ b/src/models/entities/Address.ts
@@ -10,7 +10,8 @@ import { Participant } from "./Participant";
 import { RunnerOrganisation } from "./RunnerOrganisation";
 
 /**
- * Defines a address (to be used for contact information).
+ * Defines the Address entity.
+ * Implemented this way to prevent any formatting differences.
 */
 @Entity()
 export class Address {
@@ -23,6 +24,7 @@ export class Address {
 
   /**
    * The address's description.
+   * Optional and mostly for UX.
    */
   @Column({ nullable: true })
   @IsString()
@@ -49,6 +51,8 @@ export class Address {
 
   /**
    * The address's postal code.
+   * This will get checked against the postal code syntax for the configured country.
+   * TODO: Implement the config option. 
    */
   @Column()
   @IsString()
diff --git a/src/models/entities/DistanceDonation.ts b/src/models/entities/DistanceDonation.ts
index 3103865..d263e90 100644
--- a/src/models/entities/DistanceDonation.ts
+++ b/src/models/entities/DistanceDonation.ts
@@ -4,19 +4,21 @@ import { Donation } from "./Donation";
 import { Runner } from "./Runner";
 
 /**
- * Defines a distance based donation.
- * Here people donate a certain amout per kilometer
+ * Defines the DistanceDonation entity.
+ * For distanceDonations a donor pledges to donate a certain amount for each kilometer ran by a runner.
 */
 @ChildEntity()
 export class DistanceDonation extends Donation {
   /**
-   * The runner associated.
+   * The donation's associated runner.
+   * Used as the source of the donation's distance.
    */
   @IsNotEmpty()
   @ManyToOne(() => Runner, runner => runner.distanceDonations)
   runner: Runner;
 
   /**
+   * The donation's amount donated per distance.
    * The amount the donor set to be donated per kilometer that the runner ran.
    */
   @Column()
@@ -26,12 +28,12 @@ export class DistanceDonation extends Donation {
 
   /**
    * The donation's amount in cents (or whatever your currency's smallest unit is.).
-   * The exact implementation may differ for each type of donation.
+   * Get's calculated from the runner's distance ran and the amount donated per kilometer.
    */
   public get amount(): number {
     let calculatedAmount = -1;
     try {
-      calculatedAmount = this.amountPerDistance * this.runner.distance;
+      calculatedAmount = this.amountPerDistance * (this.runner.distance / 1000);
     } catch (error) {
       throw error;
     }
diff --git a/src/models/entities/Donation.ts b/src/models/entities/Donation.ts
index 4af3485..100f0bb 100644
--- a/src/models/entities/Donation.ts
+++ b/src/models/entities/Donation.ts
@@ -6,7 +6,9 @@ import { Entity, ManyToOne, PrimaryGeneratedColumn, TableInheritance } from "typ
 import { Participant } from "./Participant";
 
 /**
- * Defines the donation interface.
+ * Defines the Donation entity.
+ * A donation just associates a donor with a donation amount.
+ * The specifics of the amoun's determination has to be implemented in child classes.
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
diff --git a/src/models/entities/Donor.ts b/src/models/entities/Donor.ts
index b92b06a..c0f914e 100644
--- a/src/models/entities/Donor.ts
+++ b/src/models/entities/Donor.ts
@@ -3,13 +3,13 @@ import { ChildEntity, Column } from "typeorm";
 import { Participant } from "./Participant";
 
 /**
- * Defines a donor.
+ * Defines the Donor entity.
 */
 @ChildEntity()
 export class Donor extends Participant {
   /**
-   * Does this donor need a receipt?.
-   * Default: false
+   * Does this donor need a receipt?
+   * Will later be used to automaticly generate donation receipts.
    */
   @Column()
   @IsBoolean()
diff --git a/src/models/entities/FixedDonation.ts b/src/models/entities/FixedDonation.ts
index 8ab366d..db53e2f 100644
--- a/src/models/entities/FixedDonation.ts
+++ b/src/models/entities/FixedDonation.ts
@@ -3,7 +3,8 @@ import { ChildEntity, Column } from "typeorm";
 import { Donation } from "./Donation";
 
 /**
- * Defines a fixed donation.
+ * Defines the FixedDonation entity.
+ * In the past there was no easy way to track fixed donations (eg. for creating donation receipts).
 */
 @ChildEntity()
 export class FixedDonation extends Donation {
diff --git a/src/models/entities/GroupContact.ts b/src/models/entities/GroupContact.ts
index d2dd367..f524863 100644
--- a/src/models/entities/GroupContact.ts
+++ b/src/models/entities/GroupContact.ts
@@ -13,13 +13,14 @@ import { Address } from "./Address";
 import { RunnerGroup } from "./RunnerGroup";
 
 /**
- * Defines a group's contact.
+ * Defines the GroupContact entity.
+ * Mainly it's own class to reduce duplicate code and enable contact's to be associated with multiple groups.
 */
 @Entity()
 export class GroupContact {
   /**
- * Autogenerated unique id (primary key).
- */
+   * Autogenerated unique id (primary key).
+   */
   @PrimaryGeneratedColumn()
   @IsInt()
   id: number;
@@ -34,7 +35,6 @@ export class GroupContact {
 
   /**
    * The contact's middle name.
-   * Optional
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -51,7 +51,7 @@ export class GroupContact {
 
   /**
    * The contact's address.
-   * Optional
+   * This is a address object to prevent any formatting differences.
    */
   @IsOptional()
   @ManyToOne(() => Address, address => address.participants, { nullable: true })
@@ -59,7 +59,7 @@ export class GroupContact {
 
   /**
    * The contact's phone number.
-   * Optional
+   * This will be validated against the configured country phone numer syntax (default: international).
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -68,7 +68,7 @@ export class GroupContact {
 
   /**
    * The contact's email address.
-   * Optional
+   * Could later be used to automaticly send mails concerning the contact's associated groups.
    */
   @Column({ nullable: true })
   @IsOptional()
diff --git a/src/models/entities/Participant.ts b/src/models/entities/Participant.ts
index 6f3554a..e2e2263 100644
--- a/src/models/entities/Participant.ts
+++ b/src/models/entities/Participant.ts
@@ -13,7 +13,8 @@ import { Address } from "./Address";
 import { Donation } from "./Donation";
 
 /**
- * Defines the participant interface.
+ * Defines the Participant entity.
+ * Participans can donate and therefor be associated with donation entities.
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
@@ -35,7 +36,6 @@ export abstract class Participant {
 
   /**
    * The participant's middle name.
-   * Optional
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -52,14 +52,14 @@ export abstract class Participant {
 
   /**
    * The participant's address.
-   * Optional
+   * This is a address object to prevent any formatting differences.
    */
   @ManyToOne(() => Address, address => address.participants, { nullable: true })
   address?: Address;
 
   /**
    * The participant's phone number.
-   * Optional
+   * This will be validated against the configured country phone numer syntax (default: international).
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -68,7 +68,7 @@ export abstract class Participant {
 
   /**
    * The participant's email address.
-   * Optional
+   * Can be used to contact the participant.
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -77,6 +77,7 @@ export abstract class Participant {
 
   /**
    * Used to link the participant as the donor of a donation.
+   * Attention: Only runner's can be associated as a distanceDonations distance source.
    */
   @OneToMany(() => Donation, donation => donation.donor, { nullable: true })
   donations: Donation[];
diff --git a/src/models/entities/Permission.ts b/src/models/entities/Permission.ts
index b95bb84..6a07312 100644
--- a/src/models/entities/Permission.ts
+++ b/src/models/entities/Permission.ts
@@ -8,7 +8,9 @@ import { PermissionAction } from '../enums/PermissionAction';
 import { PermissionTarget } from '../enums/PermissionTargets';
 import { Principal } from './Principal';
 /**
- * Defines the Permission interface.
+ * Defines the Permission entity.
+ * Permissions can be granted to principals.
+ * The permissions possible targets and actions are defined in enums.
 */
 @Entity()
 export class Permission {
@@ -20,13 +22,14 @@ export class Permission {
   id: number;
 
   /**
-   * The permissions principal
+   * The permission's principal.
    */
   @ManyToOne(() => Principal, principal => principal.permissions)
   principal: Principal;
 
   /**
-   * The target
+   * The permission's target.
+   * This get's stored as the enum value's string representation for compatability reasons.
    */
   @Column({ type: 'varchar' })
   @IsNotEmpty()
@@ -34,14 +37,16 @@ export class Permission {
   target: PermissionTarget;
 
   /**
-   * The action type
+   * The permission's action.
+   * This get's stored as the enum value's string representation for compatability reasons.
    */
   @Column({ type: 'varchar' })
   @IsEnum(PermissionAction)
   action: PermissionAction;
 
   /**
-   * Turn this into a string for exporting (and jwts).
+   * Turn this into a string for exporting and jwts.
+   * Mainly used to shrink the size of jwts (otherwise the would contain entire objects).
    */
   public toString(): string {
     return this.target + ":" + this.action;
diff --git a/src/models/entities/Principal.ts b/src/models/entities/Principal.ts
index 618e3db..f33d0be 100644
--- a/src/models/entities/Principal.ts
+++ b/src/models/entities/Principal.ts
@@ -4,23 +4,27 @@ import { ResponsePrincipal } from '../responses/ResponsePrincipal';
 import { Permission } from './Permission';
 
 /**
- * Defines a admin user.
+ * Defines the principal entity.
+ * A principal basicly is any entity that can receive permissions for the api (users and their groups).
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
 export abstract class Principal {
   /**
-  * autogenerated unique id (primary key).
+  * Autogenerated unique id (primary key).
   */
   @PrimaryGeneratedColumn()
   @IsInt()
   id: number;
 
   /**
-* permissions
-*/
+  * The participant's permissions.
+  */
   @OneToMany(() => Permission, permission => permission.principal, { nullable: true })
   permissions: Permission[];
 
+  /**
+   * Turns this entity into it's response class.
+   */
   public abstract toResponse(): ResponsePrincipal;
 }
\ No newline at end of file
diff --git a/src/models/entities/Runner.ts b/src/models/entities/Runner.ts
index 6f4033a..def167d 100644
--- a/src/models/entities/Runner.ts
+++ b/src/models/entities/Runner.ts
@@ -7,44 +7,52 @@ import { RunnerGroup } from "./RunnerGroup";
 import { Scan } from "./Scan";
 
 /**
- * Defines a runner.
+ * Defines the runner entity.
+ * Runners differ from participants in being able to actually accumulate a ran distance through scans.
+ * Runner's get organized in groups.
 */
 @ChildEntity()
 export class Runner extends Participant {
   /**
    * The runner's associated group.
+   * Can be a runner team or organisation.
    */
   @IsNotEmpty()
   @ManyToOne(() => RunnerGroup, group => group.runners, { nullable: false })
   group: RunnerGroup;
 
   /**
-   * Used to link runners to donations.
+   * The runner's associated distanceDonations.
+   * Used to link runners to distanceDonations in order to calculate the donation's amount based on the distance the runner ran.
    */
   @OneToMany(() => DistanceDonation, distanceDonation => distanceDonation.runner, { nullable: true })
   distanceDonations: DistanceDonation[];
 
   /**
-   * Used to link runners to cards.
+   * The runner's associated cards.
+   * Used to link runners to cards - yes a runner be associated with multiple cards this came in handy in the past.
    */
   @OneToMany(() => RunnerCard, card => card.runner, { nullable: true })
   cards: RunnerCard[];
 
   /**
-   * Used to link runners to a scans
+   * The runner's associated scans.
+   * Used to link runners to scans (valid and fraudulant).
    */
   @OneToMany(() => Scan, scan => scan.runner, { nullable: true })
   scans: Scan[];
 
   /**
    * Returns all valid scans associated with this runner.
+   * This is implemented here to avoid duplicate code in other files.
    */
   public get validScans(): Scan[] {
     return this.scans.filter(scan => { scan.valid === true });
   }
 
   /**
-   * Returns the total distance ran by this runner.
+   * Returns the total distance ran by this runner based on all his valid scans.
+   * This is implemented here to avoid duplicate code in other files.
   */
   @IsInt()
   public get distance(): number {
diff --git a/src/models/entities/RunnerCard.ts b/src/models/entities/RunnerCard.ts
index 49ea0da..5f48257 100644
--- a/src/models/entities/RunnerCard.ts
+++ b/src/models/entities/RunnerCard.ts
@@ -11,7 +11,9 @@ import { Runner } from "./Runner";
 import { TrackScan } from "./TrackScan";
 
 /**
- * Defines a card that can be scanned via a scanner station.
+ * Defines the RunnerCard entity.
+ * A runnerCard is a physical representation for a runner.
+ * It can be associated with a runner to create scans via the scan station's.
 */
 @Entity()
 export class RunnerCard {
@@ -23,7 +25,8 @@ export class RunnerCard {
   id: number;
 
   /**
-   * The runner that is currently associated with this card.
+   * The card's currently associated runner.
+   * To increase reusability a card can be reassigned.
    */
   @IsOptional()
   @ManyToOne(() => Runner, runner => runner.cards, { nullable: true })
@@ -32,7 +35,7 @@ export class RunnerCard {
   /**
    * The card's code.
    * This has to be able to being converted to something barcode compatible.
-   * could theoretically be autogenerated
+   * Will get automaticlly generated (not implemented yet).
    */
   @Column()
   @IsEAN()
@@ -49,7 +52,8 @@ export class RunnerCard {
   enabled: boolean = true;
 
   /**
-   * Used to link cards to a track scans.
+   * The card's associated scans.
+   * Used to link cards to track scans.
    */
   @OneToMany(() => TrackScan, scan => scan.track, { nullable: true })
   scans: TrackScan[];
diff --git a/src/models/entities/RunnerGroup.ts b/src/models/entities/RunnerGroup.ts
index a2bd585..4256f6e 100644
--- a/src/models/entities/RunnerGroup.ts
+++ b/src/models/entities/RunnerGroup.ts
@@ -9,7 +9,8 @@ import { GroupContact } from "./GroupContact";
 import { Runner } from "./Runner";
 
 /**
- * Defines the runnerGroup interface.
+ * Defines the RunnerGroup entity.
+ * This is used to group runners together (as the name suggests).
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
@@ -31,13 +32,14 @@ export abstract class RunnerGroup {
 
   /**
    * The group's contact.
-   * Optional
+   * This is mostly a feature for the group managers and public relations.
    */
   @IsOptional()
   @ManyToOne(() => GroupContact, contact => contact.groups, { nullable: true })
   contact?: GroupContact;
 
   /**
+   * The group's associated runners.
    * Used to link runners to a runner group.
    */
   @OneToMany(() => Runner, runner => runner.group, { nullable: true })
diff --git a/src/models/entities/RunnerOrganisation.ts b/src/models/entities/RunnerOrganisation.ts
index 28b90d8..8d24077 100644
--- a/src/models/entities/RunnerOrganisation.ts
+++ b/src/models/entities/RunnerOrganisation.ts
@@ -5,22 +5,23 @@ import { RunnerGroup } from "./RunnerGroup";
 import { RunnerTeam } from "./RunnerTeam";
 
 /**
- * Defines a runner organisation (business or school for example).
+ * Defines the RunnerOrganisation entity.
+ * This usually is a school, club or company.
 */
 @ChildEntity()
 export class RunnerOrganisation extends RunnerGroup {
 
   /**
    * The organisations's address.
-   * Optional
    */
   @IsOptional()
   @ManyToOne(() => Address, address => address.groups, { nullable: true })
   address?: Address;
 
   /**
- * Used to link teams to runner groups.
- */
+   * The organisation's teams.
+   * Used to link teams to a organisation.
+   */
   @OneToMany(() => RunnerTeam, team => team.parentGroup, { nullable: true })
   teams: RunnerTeam[];
 }
\ No newline at end of file
diff --git a/src/models/entities/RunnerTeam.ts b/src/models/entities/RunnerTeam.ts
index bcae3fd..e84ee9b 100644
--- a/src/models/entities/RunnerTeam.ts
+++ b/src/models/entities/RunnerTeam.ts
@@ -4,14 +4,15 @@ import { RunnerGroup } from "./RunnerGroup";
 import { RunnerOrganisation } from "./RunnerOrganisation";
 
 /**
- * Defines a runner team (class or deparment for example).
+ * Defines the RunnerTeam entity.
+ * This usually is a school class or department in a company.
 */
 @ChildEntity()
 export class RunnerTeam extends RunnerGroup {
 
   /**
    * The team's parent group.
-   * Optional
+   * Every team has to be part of a runnerOrganisation - this get's checked on creation and update.
    */
   @IsNotEmpty()
   @ManyToOne(() => RunnerOrganisation, org => org.teams, { nullable: true })
diff --git a/src/models/entities/Scan.ts b/src/models/entities/Scan.ts
index b8fc079..1b66851 100644
--- a/src/models/entities/Scan.ts
+++ b/src/models/entities/Scan.ts
@@ -9,7 +9,8 @@ import { Column, Entity, ManyToOne, PrimaryGeneratedColumn, TableInheritance } f
 import { Runner } from "./Runner";
 
 /**
- * Defines the scan interface.
+ * Defines the Scan entity.
+ * A scan basicly adds a certain distance to a runner's total ran distance.
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
@@ -22,7 +23,8 @@ export abstract class Scan {
   id: number;
 
   /**
-   * The associated runner.
+   * The scan's associated runner.
+   * This is important to link ran distances to runners.
    */
   @IsNotEmpty()
   @ManyToOne(() => Runner, runner => runner.scans, { nullable: false })
@@ -30,15 +32,17 @@ export abstract class Scan {
 
   /**
    * The scan's distance in meters.
+   * Can be set manually or derived from another object.
    */
   @IsInt()
   @IsPositive()
   abstract distance: number;
 
   /**
- * Is the scan valid (for fraud reasons).
- * Default: true
- */
+   * Is the scan valid (for fraud reasons).
+   * The determination of validity will work differently for every child class.
+   * Default: true
+   */
   @Column()
   @IsBoolean()
   valid: boolean = true;
diff --git a/src/models/entities/ScanStation.ts b/src/models/entities/ScanStation.ts
index f014da8..1df5abf 100644
--- a/src/models/entities/ScanStation.ts
+++ b/src/models/entities/ScanStation.ts
@@ -10,7 +10,8 @@ import { Track } from "./Track";
 import { TrackScan } from "./TrackScan";
 
 /**
- * ScannerStations have the ability to create scans for specific tracks.
+ * Defines the ScanStation entity.
+ * ScanStations get used to create TrackScans for runners based on a scan of their runnerCard.
 */
 @Entity()
 export class ScanStation {
@@ -23,6 +24,7 @@ export class ScanStation {
 
   /**
    * The station's description.
+   * Mostly for better UX when traceing back stuff.
    */
   @Column({ nullable: true })
   @IsOptional()
@@ -31,6 +33,7 @@ export class ScanStation {
 
   /**
    * The track this station is associated with.
+   * All scans created by this station will also be associated with this track.
    */
   @IsNotEmpty()
   @ManyToOne(() => Track, track => track.stations, { nullable: false })
@@ -38,6 +41,7 @@ export class ScanStation {
 
   /**
    * The station's api key.
+   * This is used to authorize a station against the api (not implemented yet).
    */
   @Column()
   @IsNotEmpty()
@@ -45,7 +49,7 @@ export class ScanStation {
   key: string;
 
   /**
-   * Is the station enabled (for fraud reasons)?
+   * Is the station enabled (for fraud and setup reasons)?
    * Default: true
    */
   @Column()
diff --git a/src/models/entities/Track.ts b/src/models/entities/Track.ts
index 34f3bb6..22544d0 100644
--- a/src/models/entities/Track.ts
+++ b/src/models/entities/Track.ts
@@ -1,7 +1,6 @@
 import {
   IsInt,
   IsNotEmpty,
-
   IsPositive,
   IsString
 } from "class-validator";
@@ -10,7 +9,7 @@ import { ScanStation } from "./ScanStation";
 import { TrackScan } from "./TrackScan";
 
 /**
- * Defines a track of given length.
+ * Defines the Track entity.
 */
 @Entity()
 export class Track {
@@ -23,6 +22,7 @@ export class Track {
 
   /**
    * The track's name.
+   * Mainly here for UX.
    */
   @Column()
   @IsString()
@@ -31,6 +31,7 @@ export class Track {
 
   /**
    * The track's length/distance in meters.
+   * Will be used to calculate runner's ran distances.
    */
   @Column()
   @IsInt()
@@ -38,13 +39,15 @@ export class Track {
   distance: number;
 
   /**
-   * Used to link scan stations to track.
+   * Used to link scan stations to a certain track.
+   * This makes the configuration of the scan stations easier.
    */
   @OneToMany(() => ScanStation, station => station.track, { nullable: true })
   stations: ScanStation[];
 
   /**
    * Used to link track scans to a track.
+   * The scan will derive it's distance from the track's distance.
    */
   @OneToMany(() => TrackScan, scan => scan.track, { nullable: true })
   scans: TrackScan[];
diff --git a/src/models/entities/TrackScan.ts b/src/models/entities/TrackScan.ts
index 759c3d7..45be379 100644
--- a/src/models/entities/TrackScan.ts
+++ b/src/models/entities/TrackScan.ts
@@ -12,26 +12,30 @@ import { ScanStation } from "./ScanStation";
 import { Track } from "./Track";
 
 /**
- * Defines the scan interface.
+ * Defines the TrackScan entity.
+ * A track scan usaually get's generated by a scan station.
 */
 @ChildEntity()
 export class TrackScan extends Scan {
   /**
-   * The associated track.
+   * The scan's associated track.
+   * This is used to determine the scan's distance.
    */
   @IsNotEmpty()
   @ManyToOne(() => Track, track => track.scans, { nullable: true })
   track: Track;
 
   /**
-   * The associated card.
+   * The runnerCard associated with the scan.
+   * This get's saved for documentation and management purposes.
    */
   @IsNotEmpty()
   @ManyToOne(() => RunnerCard, card => card.scans, { nullable: true })
   card: RunnerCard;
 
   /**
-   * The scanning station.
+   * The scanning station that created the scan.
+   * Mainly used for logging and traceing back scans (or errors)
    */
   @IsNotEmpty()
   @ManyToOne(() => ScanStation, station => station.scans, { nullable: true })
@@ -39,6 +43,7 @@ export class TrackScan extends Scan {
 
   /**
    * The scan's distance in meters.
+   * This just get's loaded from it's track.
    */
   @IsInt()
   @IsPositive()
@@ -48,6 +53,7 @@ export class TrackScan extends Scan {
 
   /**
    * The scan's creation timestamp.
+   * Will be used to implement fraud detection.
    */
   @Column()
   @IsDateString()
diff --git a/src/models/entities/User.ts b/src/models/entities/User.ts
index 21970c4..4cafa8d 100644
--- a/src/models/entities/User.ts
+++ b/src/models/entities/User.ts
@@ -8,26 +8,29 @@ import { UserAction } from './UserAction';
 import { UserGroup } from './UserGroup';
 
 /**
- * Defines a admin user.
+ * Defines the User entity.
+ * Users are the ones that can use the "admin" webui and do stuff in the backend.
 */
 @ChildEntity()
 export class User extends Principal {
   /**
-  * uuid
+  * The user's uuid.
+  * Mainly gets used as a per-user salt for the password hash.
   */
   @Column({ unique: true })
   @IsUUID(4)
   uuid: string;
 
   /**
-  * user email
+  * The user's e-mail address.
+  * Either username or email has to be set (otherwise the user couldn't log in).
   */
   @Column({ nullable: true, unique: true })
   @IsEmail()
   email?: string;
 
   /**
-  * user phone
+  * The user's phone number.
   */
   @Column({ nullable: true })
   @IsOptional()
@@ -35,14 +38,15 @@ export class User extends Principal {
   phone?: string;
 
   /**
-  * username
+  * The user's username.
+  * Either username or email has to be set (otherwise the user couldn't log in).
   */
   @Column({ nullable: true, unique: true })
   @IsString()
   username?: string;
 
   /**
-  * firstname
+  * The user's first name.
   */
   @Column()
   @IsString()
@@ -50,7 +54,7 @@ export class User extends Principal {
   firstname: string;
 
   /**
-  * middlename
+  * The user's middle name.
   */
   @Column({ nullable: true })
   @IsString()
@@ -58,7 +62,7 @@ export class User extends Principal {
   middlename?: string;
 
   /**
-  * lastname
+  * The user's last name.
   */
   @Column()
   @IsString()
@@ -66,7 +70,8 @@ export class User extends Principal {
   lastname: string;
 
   /**
-  * password
+  * The user's password.
+  * This is a argon2 hash salted with the user's uuid.
   */
   @Column()
   @IsString()
@@ -74,7 +79,8 @@ export class User extends Principal {
   password: string;
 
   /**
-  * groups
+  * The groups this user is a part of.
+  * The user will inherit the groups permissions (without overwriting his own).
   */
   @IsOptional()
   @ManyToMany(() => UserGroup, { nullable: true })
@@ -82,21 +88,23 @@ export class User extends Principal {
   groups: UserGroup[];
 
   /**
-  * is user enabled?
+  * Is this user enabled?
   */
   @Column()
   @IsBoolean()
   enabled: boolean = true;
 
   /**
-  * jwt refresh count
+  * The user's jwt refresh token count.
+  * Used to invalidate jwts.
   */
   @IsInt()
   @Column({ default: 1 })
   refreshTokenCount?: number;
 
   /**
-  * profilepic
+  * The user's profile picture.
+  * We haven't decided yet if this will be a bas64 encoded image or just a link to the profile picture.
   */
   @Column({ nullable: true, unique: true })
   @IsString()
@@ -104,14 +112,15 @@ export class User extends Principal {
   profilePic?: string;
 
   /**
-   * actions
+   * The actions performed by this user.
+   * For documentation purposes only, will be implemented later.
    */
   @IsOptional()
   @OneToMany(() => UserAction, action => action.user, { nullable: true })
   actions: UserAction[]
 
   /**
-   * Turn this into a response.
+   * Turns this entity into it's response class.
    */
   public toResponse(): ResponsePrincipal {
     return new ResponseUser(this);
diff --git a/src/models/entities/UserAction.ts b/src/models/entities/UserAction.ts
index 92c41f0..d22bd37 100644
--- a/src/models/entities/UserAction.ts
+++ b/src/models/entities/UserAction.ts
@@ -1,14 +1,17 @@
 import {
+  IsEnum,
   IsInt,
   IsNotEmpty,
   IsOptional,
   IsString
 } from "class-validator";
 import { Column, Entity, ManyToOne, PrimaryGeneratedColumn } from "typeorm";
+import { PermissionAction } from '../enums/PermissionAction';
 import { User } from './User';
 
 /**
- * Defines the UserAction interface.
+ * Defines the UserAction entity.
+ * Will later be used to document a user's actions.
 */
 @Entity()
 export class UserAction {
@@ -20,7 +23,7 @@ export class UserAction {
   id: number;
 
   /**
-   * user
+   * The user that performed the action.
    */
   @ManyToOne(() => User, user => user.actions)
   user: User
@@ -34,15 +37,16 @@ export class UserAction {
   target: string;
 
   /**
-   * The actions's action (e.g. UPDATE)
+   * The actions's action (e.g. UPDATE).
+   * Directly pulled from the PermissionAction Enum.
    */
-  @Column()
-  @IsNotEmpty()
-  @IsString()
-  action: string;
+  @Column({ type: 'varchar' })
+  @IsEnum(PermissionAction)
+  action: PermissionAction;
 
   /**
-   * The description of change (before-> after; e.g. distance:15->17)
+   * The description of the change (before-> after; e.g. distance:15->17).
+   * Will later be defined in more detail.
    */
   @Column({ nullable: true })
   @IsOptional()
diff --git a/src/models/entities/UserGroup.ts b/src/models/entities/UserGroup.ts
index c14f8fb..4d45a3f 100644
--- a/src/models/entities/UserGroup.ts
+++ b/src/models/entities/UserGroup.ts
@@ -9,7 +9,8 @@ import { ResponseUserGroup } from '../responses/ResponseUserGroup';
 import { Principal } from './Principal';
 
 /**
- * Defines the UserGroup interface.
+ * Defines the UserGroup entity.
+ * This entity describes a group of users with a set of permissions.
 */
 @ChildEntity()
 export class UserGroup extends Principal {
@@ -30,6 +31,9 @@ export class UserGroup extends Principal {
   @IsString()
   description?: string;
 
+  /**
+   * Turns this entity into it's response class.
+   */
   public toResponse(): ResponsePrincipal {
     return new ResponseUserGroup(this);
   }