title: How is the undo tree used in Vim?
body: <p><a href="https://stackoverflow.com/questions/1088387/what-specific-productivity-gains-does-vim-emacs-provide-over-gui-text-editors/1088705#1088705">This answer</a> says:</p>
  <blockquote>
  <p>Vim's undo/redo system is unbeatable. Type something, undo, type something else, and you can still get back the first thing you typed because Vim uses an undo tree rather than a stack. In almost every other program, the history of the first thing you typed is lost in this circumstance.</p>
  </blockquote>
  <p>This is the first I hear of this. How can I backtrack along the tree?</p>