What do you mean by Async Task in Android ?

* It is a Task which provides functionality of Background and Main Thread.

* It allows application to be performed in Background thread and Update UI element in
foreground or Main thread.

* Though Async Task can perform both background and foreground operation , multiple
application needs physical copy of Async Task class in their projects.

* So Async Task can be used in Client - Server Application.

When an Async task is executed, the task goes through 4 steps:

1. onPreExecute()
2. doInBackground()
3. onProgressUpdate()
4. onPostExecute()

In Brief , you can go through this link http://developer.android.com/reference/android/os/AsyncTask.html