Note that many of the streaming services (such as ESPN) require a compatible cable TV subscription. Others require either a cable TV subscription or have a separate subscription such as HBO and Showtime.
Note that many "tv" offering might not be available on Apple TV such as local tv broadcast and live NFL games.
Re: I currently have DirecTV and Im considering getting Apple TV
Welcome to iMore! Exactly as @SwitchBeach stated. If you get a gen 4 AppleTV and there's an app for a particular network available, you can use your DirecTV subscription to activate the content as long as the network is part of your DirecTV package. For example, you can't login to HBO Go if you have HBO.