title: difference between getChildHtml() and getChildChildHtml() in Magento
body: <p>I want to know the differences between this two functions. I understand the behavior of getChildHtml(). It returns the html of the block or all the blocks if you don´t pass any parameters.
  And I can see </p>
  
  <pre><code>getChildHtml($name, $useCache, $sorted)
  getChildChildHtml($name, $childName,$useCache, $sorted)
  </code></pre>
  
  <p>at first sight I a $useCache param that I suposed is to use cache.</p>