In this chapter, we introduced activities and fragments. Activities represent screens within your app and moving from activity to activity allows your user to navigate through your application.
Fragments are analogous to subactivities and encapsulate much of the actions and code from an activity. This allows you to easily reuse the activity logic and add multiple instances of a fragment to a single activity allowing for richer user experiences, including designing for larger screens and tablet devices. The next chapter we will focus on how to add views to our activities and fragments to make them more useful.