title: How do you 'redo' changes after 'undo' with Emacs?
body: <p><a href="http://www2.lib.uchicago.edu/keith/tcl-course/emacs-tutorial.html" rel="noreferrer">This article</a> says that "Emacs has redo because you can reverse direction while undoing, thereby undoing the undo".</p>
  
  <p>What does this mean? How can a user 'redo' with Emacs?</p>