Canon is like this really, really big gun.
Naw, just kidding. Like what was already said, official canon is what's been shown on screen: movies and tv.
However, I personally prescribe to my own personal canon, which is guided by official canon. This means when I like something from books, and other "unoffical canon," I'll include it in my own personal canon, and in my own mind, even tweak the official canon stuff to be more to my own liking.