Metadata is used to decorate the class so that it can configure the expected behavior of a class. Decorators are the core concept when developing with Angular (versions 2 and above). The user can use metadata to a class to tell Angular app that AppComponent is the component. Metadata can be attached to the TypeScript using the decorator.
@Component({ selector: 'app-root', templateUrl: './app.component.html',
styleUrls: ['./app.component.css'] })
@Component is a decorator which makes use of configuration object to
create the component and its view.