The back button reminds me of clearing cache. It is easy, but "when" is hard. With the back button, easy, but where!? [back to the app you opened? or back to th

The back button reminds me of clearing cache. It is easy, but "when" is hard. With the back button, easy, but where!? [back to the app you opened? or back to the email that triggered it? or the notification that pop'ed up? or trigger the browser back?]