What is a directive in Angular and what are the different types of directives?

In Angular, a directive is a class with a @Directive decorator that provides a way to extend the behavior of HTML elements. Directives are used to add logic and interactivity to the user interface, and they can be used to manipulate the DOM, bind events, and change styles.

There are three main types of directives in Angular:

1. Component Directives: Component directives are the most common type of directive and they are used to define components. A component directive is a directive that has a template, a class, and a selector.
2. Structural Directives: Structural directives are used to manipulate the structure of the DOM. For example, the ngIf directive can be used to conditionally show or hide an element based on a condition.
3. Attribute Directives: Attribute directives are used to manipulate the behavior and appearance of an HTML element. For example, the ngClass directive can be used to add or remove CSS classes based on a condition.

In addition to these main types, Angular also provides some built-in directives that can be used for common tasks, such as ngFor for looping over an array, ngModel for two-way data binding, and ngStyle for dynamically setting the style of an element.

Directives are a powerful feature of Angular and they provide a way to extend the functionality of HTML elements and to create reusable components that can be used throughout an application. By using directives, you can simplify the code, keep the components and the templates clean, and separate the concerns of the user interface and the business logic.