It's something I can't find anywhere, I only know that it affects everything like Luck (seen that on UESP).

Anywhere I can see what it affects and how much?

I am not sure where to find it besides UESP.

You either do less damage or your foes have more hitpoints, I'm sure of this. I can't hit down a cliff racer with a single iron arrow at maximum difficulty. It is perfectly possible to do it if you have a decent Marksman and slide the difficulty bar a bit down.

From my experience, the only thing that changes with higher difficulty is how much damage enemies do. Playing the game at 100 or -100 difficulty does not matter as long as you don't get hit.

Other things than that may be affected, but if they are, I have never noticed them at all.