Thread
Android supports standard Java Threads. You can use standard Threads and the tools from the package “java.util.concurrent” to put actions into the background. The only limitation is that you cannot directly update the UI from the a background process.
If you need to update the UI from a background task you need to use some Android specific classes. You can use the class “android.os.Handler” for this or the class “AsyncTask”
Handler
The class “Handler” can update the UI. A handle provides methods for receiving messages and for runnables. To use a handler you have to subclass it and override handleMessage() to process messages. To process Runable, you can use the method post(); You only need one instance of a handler in your activity.
You thread can post messages via the method sendMessage(Message msg) or sendEmptyMessage.
AsyncTask
If you have an Activity which needs to download content or perform operations that can be done in the background AsyncTask allows you to maintain a responsive user interface and publish progress for those operations to the user.
For more information you can have a look at these links.
http://mobisys.in/blog/2012/01/android-threads-handlers-and-asynctask-tutorial/
http://www.slideshare.net/HoangNgoBuu/android-thread-handler-and-asynctask
