What in the fn on the keyboard?

Where is the FN key on a Logitech keyboard?Last row, 6th button.

1. It is used together whit F7 key to temporarily log off the computer. 2.It is also used whit page up and page down keys either to increase or reduce the light in the screen of the functioning...

Well mine's currently in my hand as I pulled it off by mistake =@ Normally it is on the bottom left hand corner

press fn and hold then reach for Num Lock, press them together and release

function