Drupal's cache system is pretty simple. Basically, you can cache all pages trough the administration. But what happen if you need to exclude a page from caching?
If you give to your authentificated users the permission to administer menus and menu items, then all the menu including the navigation menu will be accessible. This could be a real problem, especially when you need that the authentificated users can only acces to the main menu. The module Menu Admin per Menu is here to solve this problem !