Intent object is a messaging object (instance of the android.content.Intent class) that is used to signal/activate other components such as activities, services, and broadcast receivers. E.g., activity B can register with intent A’s intent so that the bound activity B will be notified and activated when the event fires.
2. Services
A service is a UI-less component that runs in the background, usually engaged in the performance of long-running tasks
A broadcast receiver listens to special messages being broadcast by the system or individual applications
A content provider is a component that manages shared data and optionally exposes query and updates capabilities for other components to invoke