As every Org user knows, you can use Shift+Tab to cycle the folding of an Org file among OVERVIEW, CONTENTS, and ALL. That’s really handy and something I use all the time.
Yesterday, I learned something new from this Emacs Stack Exchange entry. What happens if you want to unfold, say, the first 3 headers? It’s Emacs so of course there’s a way to do that. All you have to do is specify a numeric prefix argument, \(n\), and the first \(n\) subtrees and the contents of the \(n^{\text{th}}\) level will be displayed.
You probably won’t need that very often but sometimes it’s just what you need and very useful.