Coke and coca cola are the same product, when people use the word coke it just shortens up the name. Here's a real fact,when coca cola was first developed it actually contain traces of cocaine in it, ( research it, it's true ) the drug was once legal in the U.S. physicians use to prescribe it.
its a regional thing. in the south, coke is an all inclusive term for all carbonated beverages. if you are in the north or out west and you ask a waiter what type of cokes the restaurant has, they'll look at you oddly and reply something like "regular, diet or cherry?".