Summary. With the OS X operating system of Apple computers, there is a bar across the top of the screen called the menu bar. On the far right side, there are little icons that provide instant access to some system controls and settings. This is similar to the system tray in Windows computers found in the lower right of the screen.
Example. The example pictured above shows icons for control and settings of Bluetooth, Displays, MobileMe Synchronize, Time Machine backup, Airport Wireless, Speaker volume control, battery power, day/time, and the Spotlight searching feature. Sometimes icons are installed in the menu bar by third-party applications during program installation. Others are enabled or disabled in the system preferences.
Icon Removal. A quick way to remove icons from the menu bar is to hold down the command key on the Apple keyboard and then clicking and dragging the icons away from the menu bar. The command key is usually next to the space bar and typically has an apple symbol on the key or small box with four loops on the corners. Keep in mind that removing a program icon from the menu bar may make it difficult to restore it again.
Icon Installation. Some menu bar program control icons can be found and installed from the following location: Hard Drive > System > Library > CoreServices > Menu Extras. Within the Menu Extras folder, there are about 27 items listed. When you double-click on any of these, if they are applicable for your system and configuration, then the icon will appear in the menu bar.*
CD / DVD Eject. An example of a useful control icon is the Eject icon. This lets you eject a CD from any identified CD drive. It’s quite useful for systems with more than one drive installed/connected.
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* Thanks to Bruce T. for inspiring this support page by offering the location of the Menu Extras folder.