Just what defines being crazy? What defines being insane? What's the difference?

Since the release of the new Batman movie (which, unfortunately, I have yet to see) and hearing of the madness that is the Joker, I have considered this. Personally, I have been called crazy, and a mental hospital deemed me borderline insane (no worries, kids, that was a while back! I'm worse now ^_^). I always thought of myself as being a bit off my rocker, if you know what I mean. I've always been very interested in the ways that an insane person's mind works...I would be content working in an insane asylum, just being able to analyze them.
My sister Stevie and I were talking about this...it all started with a quote I found online.

“The distance between insanity and genius is measured only by success.”  ~ Bruce Feirstein

I wholeheartedly agree: and I gave her an example. Consider Einstein, one of the greatest minds of all time. People called him insane, called him crazy...but all in all, he was really a genius. Had he not been so sucessful, he would have likely been put in the nuthouse.
But then we got to thinking...was he crazy, or was he insane? And it hit me.
Think of how a normal human being's mind operates...it wanders around different subjects when there is no immediate need, however, when it is faced with a task, it narrows itself into focusing on that particular subject. What I believe is that a person who is "crazy", rather than narrowing down and focusing on one subject when necessary, their minds constantly wander off in all directions...rarely being able to be tamed enough to focus on one specific thing that they did not begin thinking about on their own. This is how Einstein was, I believe...he didn't think about what he was supposed to think about (as is evident by the fact that he did not graduate from high school), but rather, let his mind wander into areas that normal people don't think about, or ponder about only briefly. This is also how my mind works.
As for people who are deemed "insane", I believe that they are more similar to normal people than crazy people are...they also focus their minds into one immediate subject, however the difference lies in the subject itself. An insane person's mind will be focused into areas that normal peoples' minds won't venture into, therefore deriving a certain sense of logic that isn't quite as logical to normal, sane people. The Joker is a good example of this.
This is all speculative, of course...let me know what your thoughts on it are.