What is service?

• A service does not have a visual user interface, but rather runs in the background for an indefinite period time. 
• Each service extends the Service base class. 
• Performs regular processing or handle events even after your application’s Activities are invisible, inactive, or have been closed.
• It is possible to bind to a running service and start the service if it's not already running. 
• While connected, it is possible communicate with the service through an interface.