The primary difference seems to be the elimination of the "collectible" bit. Instead of producing hundreds of cards at a time and forcing players to shell out for numerous booster packs hunting for that one special card, there's only one set of cards released at a time. So every month or so, a new set is released, and everyone who buys it gets the same cards. This levels the playing field, and reduces the financial impact on the player.

Furthermore, it allows a sort of story progression, too, which I assume is where the "living" bit comes from. In January, you might get a bunch of cards related to the Red Wedding, and be able to play out that event. Then in February, maybe you get cards for. . .wow, it's been so long since I've read those books that I can't even think of another scene. You get the idea though. Instead of collecting cards from a wide variety, you're given periodic "story based" installments. It's almost like playing D&D or something, with a new episode delivered each month.

Anyway, that's my impression on how it works, but someone who actually knows about it can feel free to correct me.