I hold no illusions that I could hang with a pro. The main difference is...there is no main difference, they do all the little things right; they do it consistently, they do it without thinking about it, they change directions mich faster/more efficiently, and they are much more physically fit, allowing them to keep it up. Serving is another big one...if you have never played somebody with a consistent kick serve that bounces at it above your head every time, it is going to STRAIGHT UP BAFFLE YOU until you figure out how to read/return it.
I have a pretty damn good forehand and backhand but all those little things listed above add up to kind of a big gulf in skill level