title: What does the `.EXT` mean in kohana index file?
body: <p>I'm a MVC n00b learning Kohana via online tutorials.</p>
  
  <p>I'm looking at a file called <code>index.php</code>.</p>
  
  <p>What is the <code>.EXT</code> for (what does it mean?) in the following line?</p>
  
  <pre><code>// Bootstrap the application
  require APPPATH.'bootstrap'.EXT;
  </code></pre>