Controllers are responsible for handling incoming requests and returning responses.

When a client sends a request to your server, the controller receives it and decides what should happen next.

In Nest.js, controllers are defined using decorators. A decorator tells Nest how a class or method should behave.

For example:

import { Controller, Get } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get()
  getAllUsers() {
    return 'List of users';
  }
}

In this example:

• @Controller('users'): defines the base route;
• @Get(): handles GET requests;
• getAllUsers(): returns a response.

When you open /users in the browser, this method is executed.

Controllers should stay simple. Their job is to:

• Receive the request;
• Call the appropriate logic;
• Return a response.

They should not contain complex logic. That logic belongs in services.