Here's some HP common Fn functions.

Hotkey combinations functions
Fn+F1 lower the brightness of screen
Fn+F2 increase the brightness of the screen
Fn+F5 switch between interior and exterior display screens and display together at the same time

Fn+F7 audio mute
Fn+F8 turn on/off built-in keyboard, this won?t affect external keyboard, if start num lock, then digital function key could be used, otherwise, cursor control is available, there?s mark on external keyboard.
Fn+F12 enter hibernating mode<br>

Fn+numlock turn on/off scroll lock.