There are a few different meanings of the word. I believe in all the resorts, they now have an area near the registration desk called lobby concierge. The CM's here can assist you with ADR's, tickets, printing boarding passes, etc. while you are on site.
In the deluxe resorts, AKL, BC, CR, GF, Poly, WL & YC, they offer a concierge or club level. When you've booked a reservation at this level, you'll have access to an itinerary planning department. These CM's will assist you with anything you need prior to your vacation. With a few e-mails or phone calls, they will take care of all your ADR's, tours, room requests, special celebrations, gift purchases, tickets, transportation, etc. When you arrive, you are typically met or escorted to a private floor or building for personal check-in. On site staff is available daily from 7am-10pm to assist you with any last minute changes or arrangements. Sometimes your room will have upgraded amenities, more space, a better view or exclusive tours offered. A concierge lounge provides snacks and drinks through out the day. Park purchases are delivered to your room instead of having to pick them up at the gift shop.
It's basically a higher level of service.