what are the types of directives?
and what are the built-in example for each of them?
there are 3 types of directives:
router-outlet) is the main building block for Angular applications, they can be used in a reusable form with a selector and inputs, or being bind to a route with params
ngIf) is used to to control if an element should be added or remove from the DOM
ngClass) is used to change specific behavior of the element applied to (with
ngClass for example to add or remove a class for the Element)