A drop down menu is horizontal list of options that each contain a vertical menu. When you roll over or click one of the primary options in a drop down menu, a list of choices will "drop down" below the main menu.
The most common type of drop down menu is a menu bar. On Windows systems, the menu bar is typically located at the top of each open window. On Macintosh systems, it is fixed at the top of the screen. When you click one of the options in the menu bar, such as "File", a list of options will appear below the menu, such as New, Open, Close, and Save. You can click any of these options to select it.
Drop down menus are also commonly used for website navigation. Many websites use drop down menus to provide users with direct links to more pages than standard navigation bars allow. For example, a news website may list several news categories in the main menu, such as Politics, Business, Sports, and Entertainment. Each of these menu options may include several subcategories. For example, the Sports menu may contain options such Baseball, Basketball, Football, Hockey, and Soccer. By selecting a specific sport within the Sports menu, you can navigate to the section you want with one click, instead of having to visit the main Sports page first.