A menu bar is a horizontal menu, or a list of the task options, which usually appears at the top of a window in a graphical user environment. This type of menu can also be called a moving bar menu, as the various options are highlighted as the mouse-directed bar or box is moved from one option to another. The bar is designed such that the clicking of the mouse on a selected option triggers the appearance of a pop-up or pull-down menu (which can also be called a cascading menu), which lists further sub-options. Highlighting a desired option using the mouse and clicking the relevant mouse key or pad will trigger the functioning of the option.

The menu bar contrasts with the so-called command-driven system, in which the command must be explicitly entered, rather than chosen from a list of possible commands. A menu-driven system, and the menu bar in particular, is intended to be simpler and easier to learn than a command-driven system. However, a command-driven system retains greater flexibility in terms of interaction with programs.