A skill is their term for adding a functionality to Alexa--not an app exactly, but in my mind sort of akin to one. I've added the Sirius XM skill, for instance. You need to enable those skills for the device to be able to do a certain task.
It's just a one-time, four hour stunt. A clever idea, good sales gimmick, and really not a problem. To the degreee that the future incorporates such devices and streaming solutions, incorporating something like this makes perfect sense.