I think the best thing to do as a starting point is to hop onto Wikipedia in one window and the features list of a MOBO on another and go one by one. Your question could literally be like peeling an onion, as the explanation one gives may use terms you don't understand as well. You'd be in a loop of confusion. At least in Wikipedia it's possible a term used to explain something may be hyperlinked so you can quickly look that up as well.
I'm not saying that Wikipedia is always right, but it's rarely completely wrong for your purposes.
There may be an FAQ out there on this as well. Simple searches will result in everything from very rudimentary explanations all the way up: http://pcsupport.about.com/od/insidethepc/ss/howitfits_2.htm
There are many great articles to be found here as well. Read reviews and you will begin to pick up the lingo using context clues.