Feature Modules

A Feature Module

// my-feature.module.ts
import { CommonModule } from '@angular/common';
import { NgModule }     from '@angular/core';

import { MyComponent } from './my.component';
import { MyDirective } from './my.directive';
import { MyPipe }      from './my.pipe';
import { MyService }   from './my.service';

@NgModule({
  imports:      [ CommonModule ],
  declarations: [ MyComponent, MyDirective, MyPipe ],
  exports:      [ MyComponent ],
  providers:    [ MyService ]
})
export class MyFeatureModule { }

Now, in your root (usually app.module.ts):

// app.module.ts
import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }    from './app.component';
import { MyFeatureModule } from './my-feature.module';

@NgModule({
  // import MyFeatureModule in root module
  imports:      [ BrowserModule, MyFeatureModule ],
  declarations: [ AppComponent ],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }