android: when to use onStart(), onStop()?

I've read several posts that describe the difference between onStart() and onResume(): onStart() is called when the activity becomes visible, onResume() is called when the activity is ready for interaction from the user. fine.

I've always just added code to onPause() and onResume(), and never bothered with onStart() and onStop().

Can anyone give some concrete examples of what you might do in onStart(), vs. onResume()? Same goes for onStop() and onPause(), how is onStop() useful? I must be missing something fundamental here.