There is a small difference, but I think that most speakers now use them in the same way. "someone" means that you are thinking of a specific person "somebody" means that there is one person, but you are not sure who it is. For example, you can say "I am looking for someone." (you know who you are looking for) or... if I have just bought a box of cookies, and they next day they are all gone, I might say "Somebody ate my cookies!" (because I do not know who did, I just know that somebody did)

I don't see any difference.

TO me: Absolutely not! >________________< Because there is no difference between "Everyone" and "Everybody"