Modularity:

Components can be snapped into fragments that enables you to make the components to be reusable in the user interfaces.

Usually they can be used together in the same activity to allow a multi-pane UI with several fragments responsible for different screen sections.

Lifecycle:

Fragments have their own lifecycle, similar to activities, with methods like onCreate, onStart, onResume, and so on.

They are typically hosted within an activity, and their lifecycle is tied to the hosting activity.

UI Components:

Fragments can have their own UI components defined using XML layout files.

They can include elements like buttons, text fields, and more.

Fragment Transactions:

Fragments are added, replaced, or removed dynamically through fragment transactions.

Fragment transactions are managed by the FragmentManager and are used to change the content of an activity dynamically.

Communication Between Fragments:

Fragments can communicate with each other and with their hosting activity.

Communication can be achieved using interfaces or through the FragmentManager when fragments are hosted by the same activity.

Back Stack:

Fragment transactions can also be provided with back stack if required which makes the fragment similar to the back stack activity.

Dynamic UI:

In this case, fragments are useful when working with responsiveness in context with UI, particularly when the chosen layout should be suitable for different screen sizes and orientations.

Here's a simple example of using a fragment:

                      
                        public class MyFragment extends Fragment {
                            @Override
                            public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
                                // Inflate the layout for this fragment
                                return inflater.inflate(R.layout.fragment_layout, container, false);
                            }
                        
                            // Other fragment-specific methods can be overridden as needed
                        }                                                
                      
                    

                      
                        import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment

class MyFragment : Fragment() {
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_layout, container, false)
    }

    // Other fragment-specific methods can be overridden as needed
}