I'm genuinely curious.

I was raised with a very technical understanding of sex organs and their associated parts. I have no problem saying vagina or penis but a lot of the people i associate with seem to pull out the pet-names that are cutesy or just plain weird.
What do you call your "private parts"?
How about the opposite sex's parts?
Why do you use those terms as your preferred as opposed to other terms?
As a thank you, here's a bit of NSFW penis song:
http://www.youtube.com/watch?v=CcP8sVjZ5qg