You can do the same thing with your Blue Ray Player, or your Game System, or dedicated devices by users like ROKU etc... Again, Apple TV makes no sense to me.
AirPlay. I downloaded an album to my phone, AirPlay through my receiver to listen to it without tying my phone up to a wire plugged in to the receiver. One great advantage I have found for it, and I just got a Smart TV, smart BD, and have a WDTV Live Hub.