title: Magento Tree Node Collection
body: <p>I am looking for someone that can explain the concept of a "tree" a "node" and a "collection"
  in terms of Magento specifics. For example, in the below code getStoreCategories() method will return an instance of Varien_Data_Tree_Node_Collection which is enumerable and $child will be an object of type Varien_Data_Tree_Node. I'm asking in general, what does Magento mean by Tree, Node, and Collection.</p>
  
  <pre><code>foreach ($this-&gt;getStoreCategories() as $child) {
              if ($child-&gt;getIsActive()) {
                  $activeCategories[] = $child;
              }
  
          }
  </code></pre>
  
  <p>Thank you!</p>