According to what I've read, and I could be wrong, "vanilla" means traditional conventional missionary position sex. The opposite of vanilla is chocolate, which encompasses everything from light kink to down and dirty full-on bondage, S&M, etc.
I have also heard it described that vanilla sex is het and chocolate sex is homosexual, but to me, that sounds like the person is trying to say homosexual sex is unconventional, unnatural, etc, and I don't like that.
I'm bi, and I've probably tried most of the normal stuff and even a little light kink, but right now, the thing that really gets my motor running is my super smart, super sexy guy. He came home from Karate the other night and he looked so hot in that gi...and the v-neck is so convenient for pulling aside so I can... *coughs*
That's probably more than you wanted to know.
At any rate, I think sexual experimentation is cool. As long as no one gets hurt (non-consensually hurt, anyway) it's all good. Personally, pain doesn't do anything for me, but what consenting adults do with or to each other is all copacetic.
Of course, I'm monogamous with my sweet guy, so all experimentation is now being conducted with him.