HP and other computer manufacturers use function (fn) keys on compact keyboards to combine two keyboard functions into one in order to save on space. They are typically labeled F1 through F12.
In order to access default functions like mute sound, increase volume, connect projector, open web browser and open help window among others; HP users have to press down and hold the fn key while pressing any of the F1 to F12 keys. Advanced BIOS options can be used to reconfigure the function keys, thus eliminating the need to press and hold the fn key. The function key works in a similar manner to the shift key.