All menus can contain two main types of menu items: command items and submenu items. When the user chooses a command item, the menu immediately posts a message to the parent window. When the user selects a submenu item, the menu displays a submenu from which the user may choose another item. Since a submenu window also can contain a submenu item, submenus can originate from other submenus.

When the user chooses a command item from a menu, the menu system posts a WM_COMMAND, WM_SYSCOMMAND, or WM_HELP message to the owner window, depending on the style bits of the menu item.

Applications can change the attributes, style, and contents of menu items, and insert and delete items at run time, to reflect changes in the command environment. An application also can add items to or delete items from the menu bar, a pop-up menu, or a submenu. For example, an application might maintain a menu of the fonts currently available in the system. This application would use graphics programming interface (GPI) calls to determine which fonts were available and, then, insert a menu item for each font into a submenu. Furthermore, the application might set the check-mark attribute of the menu item for the currently chosen font. When the user chose a new font, the application would remove the check-mark attribute from the previous choice and add it to the new choice.