What is a Service?

A service is an Android component that lives independently from any other components. Activities may come and go, but services can stick around.

A Service is not a separate process, it runs in the same process as the application it is part of.
A Service is not a thread.

Mostly Service is mistaken to be running in separate process but its always part of the main application process. If you want it to be run separately then use <a href="http://lifeasanandroiddeveloper.blogspot.com/2011/11/what-is-async-task.html">AsynTask</a> or<a href="http://developer.android.com/reference/android/app/IntentService.html"> IntentService</a>