I think it means Order Management System. Best Buy employees have access to it on registers and it lets them order items for customers directly from the warehouse. The ordered items can be shipped to your home or any Best buy store for pickup. The big advantage is buying stuff that is out of stock online/in-store or using Gamer coupons on games out of stock in-store. The warehouse might not have any inventory left for certain items, so it does not work all the time.