Retroactive Continuity (i.e., how we explain away all those nasty contradictions in Star Wars): http://starwars.wikia.com/wiki/Retcon
"Official Levels of Canon" (I'm not sure how official they mean when they say official, though):
http://starwars.wikia.com/wiki/EU#Official_levels_of_canon
Keep following links and you'll find lots of fascinating stuff that'll distract you from studying for hours.
[size=1]"So the woman asked me what I wanted on the sandwich and I said I do not care it is for a duck, and she was like oh then it's free. I was not aware that ducks eat for free at Subway. It's like give me a chicken fajita sub, but don't worry about ringing it up, it is for a duck.”
-Mitch Hedberg
[/size]