Buyers represent real-world legal entities to which the Seller offers Product Catalogs and from which the Seller receives Orders. Buyers contain many of the same things as Sellers (Users, Groups, Addresses) and much more, including Cost Centers, Spending Accounts, and Approval Rules. Assignments are prevalent concept. Most "things" can be assigned to a User, Group, or entire Buyer organization. Plan ahead, and use Groups to your advantage here. For example, if you assign 100 Addresses directly to 50 Users, you are going to need to create 100 additional assignments every time you add a new User. Or, 50 more assignments for every new Address. With careful planning, Groups can save you from "assignment hell".