You can add the following menu types to the panels:
Menubar – You can access almost all of the standard applications, commands, and configuration options from the the menubar. It contains the Applications, Places, and System menus.
Main menu – The Main menu contains similar items as the menubar but organizes them into one menu instead of three.
Submenus – You can add a submenu of the menubar or Main menu to the panel. For example, you can add the Games submenu of the Applications menu to the panel.