Crossfire/sli question from a newbie

hello all i have a question regarding crossfire/sli motherboards. what would qualify a motherboards to be able to do CF or sli? for example i see some MB's with stuff like pci 2.0 x16  2 (x16, x4)   or (x8,x8) or (x16,x16)   etc.

what is considered to be an actual CF/sli MB?

apologize if it sounds like a dumb question but while i love electronics and all i still have very basic knowledge and would like to learn more. thanks in advance :)

Not too sure on what you're saying but,

Certified SLI/CrossFireX mobo's will be branded on the box "Supports SLI" , "Supports CrossFireX"

MSI Mpower Z77 ;) Lovely board and Sli/ crossfirex certified!

well i see plenty of motherboards with 2 pci express 2.0 but in parentheses they have stuff like what i have posted above. i guess it is the speed of the slots maybe? i read someone said to have at least x8,x8 for crossfire or sli