In addition to the normal Apple itunes store content to watch/buy/rent, the Apple TV app on Samsung TV has some channels for networks like HBO, Showtime, etc. On my Apple TV device, for example, it allows me to watch content on those kinds of TV channel apps (e.g. HBO GO, Showtime Anytime, NBC, AMC, etc.) with my own provider subscription.
Unless I'm missing something, on the Samsung Apple TV app, there doesn't appear to be a way to tie some of those kinds of channels to an existing subscription. It instead wants me to pay for it through my Apple account, which of course, is pointless. I'm figuring the lack of this feature is a decision by Apple, though, as a way to drive more revenue through iTunes store subs. No thanks.