A fragment is a new framework component that allows us to separate distinct elements of an activity into self-contained modules that define their own UI and lifecycle. To create a fragment, we must extend the Fragment class and implement several lifecycle callback methods, similar to an Activity. We can then combine multiple fragments in a single activity to build a multi-pane UI in which each pane manages its own lifecycle and user inputs.

We can also use a fragment without providing a UI and instead use the fragment as a worker for the activity, such as to manage the progress of a download that occurs only while the activity is running.

Features of Fragment:

1. Fragments are self-contained and you can reuse them in multiple activities

2.  Add, remove, replace and animate fragments inside the activity

3.  We can add fragments to a back stack managed by the activity, preserving the state of fragments as they are changed and allowing the user to navigate backward through the different states

4.  By providing alternative layouts, you can mix and match fragments, based on the screen size and orientation

5. Fragments have direct access to their container activity and can contribute items to the activity’s Action Bar