The simplest answer is @Component annotation convert any typescript class to a angular2 component. Any typescript class annotated as @Component({}) is angular2 component. As you can see in the previous answer, 2 classes are annotated with @Component. The Component takes a json object as parameter to tell angular2 what behavior of the component will be.
@Component({
selector: 'my-app', //will be user in html as tag/attribut
template: ` //the html injection etc
<my-cmp type="Static Type"></my-cmp>
<my-cmp [type]="dynamicType + dynamicTypeIndex"></my-cmp>
`
})
export class AppCompoment { //we exported this class/component so that it can be imported
}