title: In Vim, what is the "alternate file"?
body: <p>I just ran <code>:help registers</code> in Vim and noticed that <code>#</code> 'contains the name of the alternate file'.</p>
  
  <p>I have seen an example for renaming files that goes like this:</p>
  
  <pre><code>" Save the current file, foo.txt, as bar.txt
  :w bar.txt
  " Start editing bar.txt
  :e#
  </code></pre>
  
  <p>So apparently in that case, the file you just saved out is the "alternate file."</p>
  
  <p>Can someone give me a more general definition for the "alternate file" and what else you might use it for?</p>