Components

Components define views, which are sets of screen elements that Angular can choose among and modify according to your program logic and data.

Components use services, which provide specific functionality not directly related to views.

Service providers can be injected into components as dependencies, making your code modular, reusable, and efficient.

Every Angular application has at least one component, the root component that connects a component hierarchy with the page document object model (DOM).

Each component defines a class that contains application data and logic, and is associated with an HTML template that defines a view to be displayed in a target environment.

The @Component() decorator identifies the class immediately below it as a component, and provides the template and related component-specific metadata.

Ref: angular.io