When you start your app, onCreate(), onStart(), onResume() gets called where onCreate() can be used like a constructor. When you move to some other app and your screen is partially blocked, onPause() is called, if your screen is fully obscured, onStop() is called. When you come back to your app from another app, onRestart(), onStart(), onResume() is called. When you press back button inside your app, onDestroy() gets called and your Activity is destroyed. Use the Activity lifecycle wisely and you’ll making amazing apps.