title: Magento: app/code/local vs. app/etc/modules
body: <p>A lot of literature on the web teaches the difference between app/design and skin
  and goes to great length to describe all of their subdirectories and how they relate
  to each other. However I am struggling with another part of the Magento directory tree.
  What is the difference in the purpose of the app/code/local and app/etc/modules .
  While custom code goes in app/code/local is app/etc/modules where the code needs
  to be declared to actually appear in the admin panel?</p>
  
  <p>Thanks.</p>