Three of the four component types—activities, services,
and broadcast receivers—are activated by an asynchronous
message named intent. Intents bind individual components to
each other at runtime no matter the component belongs to the
same application. An intent can create with an Intent object,
which defines the messages by which can activate either a
specific component or a specific type of component. For
activities and services, an intent defines the action to perform
and may specify the URI of the data to act ion. For broadcast
receivers, the intent simply defines the announcement being
broadcast. The other component type, content provider, is
not activated by intents. Rather, it is activated when targeted
by a request from a Content Resolver.