Every Activity within an app runs within the App Process, but each Activity is also subject to its own lifecycle. These are methods that are triggered by the platform when the Activity is about to change states, for example, when the user exits the Activity temporarily to use another Activity (whether it's in the same application, or another one). Fragment objects are also subject to a lifecycle, and while it mostly follows the same pattern as the Activity lifecycle, it also has the notion of being "attached" and "detached" from its parent Activity.
The following workflow explains the Activity lifecycle in detail:
