What does this constant in the parameter do?
<p>It's a cross fade slide show. I don't understand what this does in the code below: <code>rotatePics(1);</code></p>

<p>HTML</p>

<pre><code>&lt;div id="photos"&gt;
  &lt;img alt="Glendatronix" src="../../images/glenda_200.jpg" /&gt;
  &lt;img alt="Darth Fader" src="../../images/fader_200.jpg" /&gt;
  &lt;img alt="Beau Dandy" src="../../images/beau_200.jpg" /&gt;
  &lt;img alt="Johnny Stardust" src="../../images/johnny_200.jpg" /&gt;
  &lt;img alt="Mo' Fat" src="../../images/mofat_200.jpg" /&gt;
&lt;/div&gt;
</code></pre>

<p>JS</p>

<pre><code>$(document).ready(function() {
  rotatePics(1);
}

function rotatePics(currentPhoto) {
  var numberOfPhotos = $('#photos img').length;
  currentPhoto = currentPhoto % numberOfPhotos;
  $('#photos img').eq(currentPhoto).fadeOut(function() {
     // re-order the z-index
     $('#photos img').each(function(i) {
        $(this).css(
          'zIndex', ((numberOfPhotos - i) + currentPhoto) % numberOfPhotos
        );
     });
     $(this).show();
    setTimeout(function() {rotatePics(++currentPhoto);}, 4000);
  });
}
</code></pre>
