High Quality Content by WIKIPEDIA articles! Fn, or `Function`, is a modifier key on many keyboards, especially on laptops, used in a compact layout to combine keys which are usually kept separate. It is typically found on laptops, since a full-sized keyboard would be difficult to fit in a laptop chassis. It is also found in many full-sized `multimedia` and `office` keyboards, named F-Lock key. It is mainly for the purpose of changing display or audio settings quickly, such as brightness, contrast, or volume, and is held down in conjunction with the appropriate key to change the settings.