What is the purpose of `*ngIf` directive?

Sometimes an app needs to display a view or a portion of a view only under specific circumstances. The Angular *ngIf directive inserts or removes an element based on a truthy/falsy condition. Let's take an example to display a message if the user age is more than 18:

Note: Angular isn't showing and hiding the message. It is adding and removing the paragraph element from the DOM. That improves performance, especially in the larger projects with many data bindings.