DTO stands for Data Transfer Object.

A DTO is used to define the structure of data that your application receives or sends. Instead of using any or defining types inline, you create a separate class that describes the expected data.

Here is an example:

export class CreateUserDto {
  name: string;
  age: number;
}

Now use this DTO in your controller:

import { Controller, Post, Body } from '@nestjs/common';
import { CreateUserDto } from './create-user.dto';

@Controller('users')
export class UsersController {
  @Post()
  createUser(@Body() body: CreateUserDto) {
    return body;
  }
}

Here is what is happening:

• CreateUserDto: defines the shape of the data;
• @Body(): extracts the request data;
• CreateUserDto: ensures the data follows a specific structure.

DTOs help you:

• Keep data consistent;
• Avoid repeating type definitions;
• Make your code easier to read and maintain.

Instead of describing data in multiple places, you define it once and reuse it.