Directives
- Provide program logic
- Use directives to manipulate the DOM (add element, remove element, change class and style)
NgFor
- Prefix the directive with *, whenever it modifies the structure of DOM by adding or removing element
courses = ["course1", "course 2", "course 3"]
<ul>
<li *ngFor="let course of courses">{{course}}</li>
</ul>