You wonder how kids on the playground learn about such things and tell you? Yeah, well, in my neck of the woods... I was kinda the kid that informed everyone. I was the kid that ruined Santa Claus for everyone, taught everyone what sex was, what "gay" actually meant, etc. Having a very liberal upbringing kinda makes you... informed early on... and I was very social as a child. :D
As for when I learned what it was, I really couldn't tell you. I didn't really know any nuts and bolts about it, but I've always known the male anatomy went into the female anatomy and that's how babies are made. As hard as I try, I can't remember exactly where I first learned that. Everything else I learned about sexual things I learned from a childhood best friend who was a little over a year older than me as well as the school bus. I don't care what you say, the bus was the place you learned about and participated in smut.
So in a way, they never really had to give me the talk. They let me learn naturally. Though my mom always said I could come to her if I ever had any questions or just wanted to talk about things. Never really did, but it was nice to know she cared enough back then. Funny that they never thought to teach me about puberty though... that caught me off guard. XD