Android SDK 3.0 provide Fragments API for Honeycomb. A Fragment represents a behavior or a portion of user interface in an Activity. You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities. You can think of a fragment as a modular section of an activity, which has its own lifecycle, receives its own input events, and which you can add or remove while the activity is running.
Now Google have released a static library that exposes the same Fragments API (as well as the new LoaderManager and a few other classes) so that applications compatible with Android 1.6 or later can use fragments to create tablet-compatible user interfaces.
This library is available through the SDK Updater; it’s called "Android Compatibility package".
- Android Developers Blog: Fragments For All