A menu is arranged in a hierarchy. At the top level of the hierarchy is the menu bar; menus drop down from the menu bar, and at the lower levels are submenus. A menu bar is sometimes called a top-level menu, and the menus and submenus are also known as pop-up menus.
A menu item can either carry out a command or open a submenu. An item that carries out a command is called a command item or a command.
An item on the menu bar almost always opens a menu. Menu bars rarely contain command items. A menu opened from the menu bar drops down from the menu bar and is sometimes called a drop-down menu. When a drop-down menu is displayed, it is attached to the menu bar. A menu item on the menu bar that opens a drop-down menu is also called a menu name.
The menu names on a menu bar represent the main categories of commands that an application provides. Selecting a menu name from the menu bar typically opens a menu whose menu items correspond to the commands in a given category. For example, a menu bar might contain a File menu name that, when selected by the user, activates a menu with menu items such as New, Open, and Save.
Only an overlapped or pop-up window can contain a menu bar; a child window cannot contain one. If the window has a title bar, Windows positions the menu bar just below it. A menu bar is always visible. A submenu is not visible, however, until the user selects a menu item that activates it. For more information about overlapped and pop-up windows, see General Window Styles.
Each menu must have an owner window. Windows sends messages to a menu's owner window when the user selects the menu or chooses an item from the menu. These messages are described in Messages Used with Menus.