On any Joomla! website you can create as many menus as you want. The default sample site that you installed in Chapter 2 is a good example as it contains no fewer than six menus. On the home page four of those are shown: the horizontal Top Menu, the Main Menu, the Resources Menu, and the Key Concepts Menu. In the backend, all of the menus are listed in the Menu Manager (Menus | Menu Manager).
At least one menu, the Main Menu, is needed for Joomla! to function properly. The other ones, such as the Top Menu (the top horizontal menu) and the User Menu (a menu that's only visible after users have logged in), are only there to showcase Joomla!'s menu possibilities. In real life you'll probably just confuse your visitors with that amount of navigation options popping up on different pages and places.
However, it's great to be able to create as many menus as you like. This allows you to set up different menus for different functions and different users. You can have...