sli newbie here...wanna ask ho to refine quad sli or quad crossfire? does it mean u take quad gfx cards and sli it together, or take 2 gtx 590 to sli...since it has dual gpu...2x590 got 4 gpu core=quad core=quad sli?

i wonder if i use one gtx 295 or gtx 590...also can call sli? since 2 gpu there...just asking...
btw...sli option do depends on games...but how? does it means some games cannot fully utilize all the gpu? just wonder...