Heres the difference bro.
PlayStation 4 — This is the PS4 most likely to be included in some kind of extra bundle with more accessories and games. This is also the only PlayStation 4 that comes in white right now. If you're looking for a PS4 and price is a big point of concern, you probably want to stick with the original.
Slim PlayStation 4 — This is the PS4 you will see the most of on shelves this year, and it's the nicer looking of the three. If you care about that sort of thing, or you're just rushing in to grab a PS4 and nothing else, this is the version you want.
PlayStation 4 Pro — If you own a 4K television, or you plan to own one before long, this is the PlayStation 4 you want. It'll last the longest, and be able to offer the most over time.