The above picture shows the sub menu of the Forums main menu item.
Currently on Forum Box, there are sub menus for four of the main menu items, they are: Forums, Blogs, Gallery, Calendar and Members.
To access the sub menus, hover your cursor above one of the main menu items as mentioned above, but don't click on that item, otherwise you will enter the main page for that item. Keep your mouse cursor hovered over the main menu item and a drop down menu will appear, this is the sub menu.
Sub Menus contain different information and can change depending on how you use the site. As an example, if you create a album in the Gallery, a "My Albums" item will appear in the sub menu for Gallery. If you have not created any albums, you will not see this option in the Gallery sub menu.