Special Edition and Anniversary Edition

Hi friends. Steam has some cool discounts now, and I'm interested in picking up Skyrim. I've never played it, and I don't really understand what the difference between special edition and anniversary edition is. I've tried looking it up, but people just say that the difference is that the anniversary edition has cc content installed, and I have no clue what that means. Can someone dumb it down for me? Is the anniversary edition worth it at all? Or is it just some extra stuff that I won't really need?

Thanks.