why we use moduleId:module.id in angular2

relative assets for components, like templateUrl and styleUrls in the @Component decorator.
moduleId is used to resolve relative paths for your stylesheets and templates as it says in the documentation.
Without Module ID

@Component({
  selector: 'my-component',
  templateUrl: 'app/components/my.component.html',
  styleUrls:  ['app/components/my.component.css'] 
})

With Module ID

@Component({
  moduleId: module.id,
  selector: 'my-component',
  templateUrl: 'my.component.html', 
  styleUrls:  ['my.component.css'] 
})