title: How does virtualenv work?
body: <p>I checked the <em>activate</em> script and it looks to me all it does is:</p>
  
  <ul>
  <li>set VIRTUAL_ENV env</li>
  <li>append $VIRTUAL_ENV/bin in front of PATH</li>
  </ul>
  
  <p>How does <code>virtualenv</code> provide that magical virtual environment by these? What do I miss?</p>