Angular Modules, also known as NgModules, have been introduced in Angular 2 RC5 and are a great and powerful way to organize and bootstrap any Angular application; they help developers consolidate their own set of components, directives, and pipes into reusable blocks.

Every Angular application since v2 RC5 must have at least one module, which is conventionally called root module and thus given the AppModule class name.

AppModule is usually split into two main code blocks:

• A list of import statements, pointing to all the references (in the form of TS files) required by the application.
• The root NgModule declaration, which--as we can see--is basically an array of named arrays, each one containing a set of Angular objects that serves a common purpose: directives, components, pipes, modules, providers, and so on. The last one of them contains the component we want to bootstrap, which in most scenarios--including ours--is the main application component, the AppComponent.