MacBook Air Magic Keyboard with Touch ID
The function keys along the upper edge of the Magic Keyboard keyboard provide shortcuts for common functions, such as increasing the volume or screen brightness. Touch ID (the power button) is located on the right side of the function keys. After you set up Touch ID, you can use your fingerprint to unlock MacBook Air and make purchases from the App Store, Apple TV app, and Book Store, and on websites using Apple Pay.
Touch ID (power button): Press to turn on your MacBook Air (or just lift the lid or press any key). When you first start up or restart the computer, you need to log in by typing your password. You can set up Touch ID during setup, or later in the Touch ID pane of System Preferences. After setup and initial login, whenever you’re asked for your password, you can just place your finger lightly on the Touch ID sensor to authenticate.
You can also use Touch ID to make online purchases securely with Apple Pay. For more information about Touch ID, see Set up your Mac. For more information about Apple Pay, see Use Apple Pay on your Mac.
Note: To turn off your MacBook Air, choose Apple menu 
> Shut Down. To put your MacBook Air to sleep, choose Apple menu > Sleep.
Many system functions can be accessed through the function keys.
Brightness keys (F1, F2): Press
or 
to decrease or increase the brightness of the screen.Mission Control key (F3): Press
to view what’s running on your MacBook Air, including all your spaces and open windows.Launchpad key (F4): Press
to instantly see all the apps on your MacBook Air. Click an app to open it.Keyboard illumination keys (F5, F6): Press
or 
to decrease or increase the brightness of the keyboard.Media keys (F7, F8, F9): Press
to rewind, 
to play or pause, or 
to fast-forward a song, movie, or slideshow.Mute key (F10): Press
to mute the sound from the built-in speakers or 3.5 mm headphone jack.Volume keys (F11, F12): Press
or 
to decrease or increase the volume of sound from the built-in speakers or 3.5 mm headphone jack.Function (Fn) key: Each function key (on the top row) can also perform other functions—for example, the F11 key can hide all open windows and show the desktop. Hold down the Fn key while you press a function key to trigger the action associated with the key.
Tip: Press the Fn key twice to turn on dictation, which lets you dictate text wherever you can type (for example, in Messages, Mail, Pages, and many other apps).
Set keyboard preferences. In System Preferences, click Keyboard, then click the buttons at the top to see the available options.
Learn about keyboard shortcuts. You can press key combinations to do things on your MacBook Air that you’d normally do with a trackpad, mouse, or other device. For a list of commonly used shortcuts, see Keyboard shortcuts on your Mac.