If you really want the full explanation...
1. I learned about sex when I was 6, technically speaking. We had this whole sex education thing called Learning About Myself and Others that was a regular thing throughout elementary school. It didn't cover the "romantic" aspects, but I knew where babies really came from and what a menstrual period was and whatnot.
2. I went through puberty pretty early anyway... I started developing boobs around 9 years old and got my period when I was 11. *shrug*
3. However, everything I knew about sex, whether from sex ed or from the tales of my girlfriends (my best friend lost her virginity at 11) revolved around the general concept of sticking something in one's vagina. Nobody ever really mentioned the concept of the clitoris, and it wasn't until I was bored one day and did some link-surfing on the topic of mastubation that it all clicked, so to speak.
So, yeah. Make of it what you will.
Peace & Luv, Liz