A menu provides a space-saving way to let the user choose one of several options. Other components with which the user can make a one-of-many choice include combo boxes, lists, radio buttons, spinners, and tool bars.
Menus are unique in that, by convention, they aren't placed with the other components in the UI. Instead, a menu usually appears either in a menu bar or as a popup menu. A menu bar contains one or more menus and has a customary, platform-dependent location — usually along the top of a window. A popup menu is a menu that is invisible until the user makes a platform-specific mouse action, such as pressing the right mouse button, over a popup-enabled component. The popup menu then appears under the cursor.