When on, the Arrow keys scroll the screen regardless of the current cursor location. This key is rarely used for its intended purpose, if at all. See PC keyboard. THIS DEFINITION IS FOR PERSONAL ...

To know if the scroll lock key is turned on, look for a light on your keyboard’s scroll lock button. To disable the scroll lock button, press the scroll lock button. When the light is turned off ...

That allows the keyboard to display the status of the caps lock, num lock and scroll lock keys instead of forcing the user to take an non-intuitive glance at a transceiver located elsewhere.