The Fn (function) key on a laptop computer allows you to access hardware and software functions via keyboard shortcuts. The Fn key is usually used in conjunction with the numbered "F" keys at the top of the keyboard.
Laptop computers usually have hardware features that you wouldn’t find on desktop PCs, such as the ability to alter the screen brightness, put the laptop into sleep mode, or toggle features such as Wi-Fi.
Keyboard shortcuts using the Fn key allow you to access these features directly.
Common functions accessed via the Fn key include brightness, volume and features such as Bluetooth.
Another widespread use of the Fn key is to switch the display output between the laptop screen and an external display--frequently used to display presentations on projectors or external monitors.
Sometimes Fn key combinations are linked to manufacturer-specific software on the laptop and switch between operating modes; for example, a mode to conserve battery and another for maximum processing power.