When wearing a fullplate, does it absorb opponent blows, or make them harder to hit you? And vice versa

It's supposedly the former, but the NWN graphic engine shows it as the latter, so whatever you want.

Absorb is a misleading word, so you could say it's actually neither.

If fullplate absorbed the impact, you could reasonably say that if you hit someone hard enough there would still be some damage dealt. This is what we call Damage Reduction, which is nothing to do with AC.

The fullplate is designed in such a way as to deflect glancing blows away from the body, making them deal no damage whatsoever.

So, if you have say, 20 dex and you wear leather armor, the armor is relying on you to move out of the way more than the armor will protect you.

With fullplate, all you got to do is stand there and the fullplat ewill provide the +8 protection ncssary, Am I correct?

Yes.

Though the fullplate allows for a +1 Dex bonus from 12 Dex. So the fullplate does allow the wearer to dodge very slightly, so you're not just standing there. 10 Dex, maybe we can say you're making no effort to avoid blows, and 8 Dex, we can say you're so clumsy you don't know how to move without making yourself an easy target.