My first concierge stay is still more than a week away, but I think I can answer.
Each concierge serves stuff from its restaruants. So AKL Concierge has stuff from Jiko and Boma, the Poly has stuff from their eateries, et, etc.
Sometimes you get a robe, sometimes slippers, sometimes a newspaper, you get special concierge pre-planning, sometimes you can get a hard o gt resevation, and you get snacks and bottled water and access to the concierge lounge.