Application

HTTP Server - NestFactory.create() with request/response capabilities.
Microservices - NestFactory.createMicroservice() similar to HTTP servers, but allows using other transport protocols instead of HTTP, even internal network communication.
Application - NestFactory.createApplicationContext() any application without a network listener.

Module

@Module({})

The different building blocks of an application.

There must always be one Root Module.

They take in an object with all their dependencies.

They can also export Providers so other modules can use them.

@Controller()

Classes used exclusively for handling requests, thanks to HTTP decorators (@Get, @Post, etc).

Used by Modules

@Injectable()

A class that can be injected into others as a dependency.