OS X Mountain Lion: What’s in the menu bar?
The menu bar runs along the top of the screen. You can use the icons and menus in the menu bar to check status, choose commands, or perform tasks.
The left end of the menu bar contains menus for the app you’re currently using.
The name of the app appears in bold next to the Apple menu. There are several other app menus, often with standard names such as File, Edit, Format, Window, and Help. Many of the commands in these menus are standard in all apps. For example, the Open command is usually in the File menu and the Copy command is usually in the Edit menu.
The right end of the menu bar contains “status menus,” which are represented by icons.
These menus show the status of your computer or give you quick access to certain features—for example, you can quickly turn on Wi-Fi, turn off Bluetooth, or mute your computer’s volume.
You can add some icons to the right end of the menu bar. For example, you can show a volume slider in the menu bar by selecting a checkbox in the Sound pane of System Preferences. You can also add a status icon for some apps to the menu bar when you install the app.
To rearrange the status menu icons, hold down the Command (⌘) key while dragging the icons. To remove an icon from the menu bar, hold down the Command key and drag the icon out of the menu bar.