I am working on the project, which was started by someone else. There are two interface files in the model folder def and dto. The difference between def and dto interface files is not clear to me. Could any expereince developer let me know what is the difference and when and how to use dto instead of def and viceversa. Thanks in advance.

vendor-def.interface.ts:

import { SourceType, VendorType } from '../shared/enums/vendor-type.enum';

export interface VendorDef {
  vendorId: string;
  companyCode: string;
  name: string;
  acronym: string;
  alias: string;
  legalId: string;
  vendorType: VendorType;
  sourceType: SourceType;
  fiscalCode: string;
}


export interface VendorFormDef {
  sourceType: SourceType;
  companyCode?: string;
  previousMainCompany?: string;
}

export interface InUsageDef {
  acronym: boolean;
  legalId: boolean;
  fiscalCode: boolean;
}

vendor-dto.interface.ts

import { SourceType, VendorType } from '../shared/enums/vendor-type.enum';

export interface VendorDto {
  data: VendorDataDto[] | VendorDataDto;
  errors?: VendorErrorsDto;
}

export interface VendorDataDto {
  attributes: VendorAttributesDto;
  id: string;
}

export interface VendorErrorsDto {
  code: string;
  title: string;
  detail: string;
}

export interface VendorCreateDto {
  companyCode: string;
  name: string;
  acronym: string;
  legalId: string;
  fiscalCode: string;
  vendorType: VendorType;
  sourceType: SourceType;
}