There are two type of users in Activation center: Administrators and Clients (end users).
Administrator users are actual managers of activation center. They are working in administrators interface and are granted "Admin" role. By default, these users are part of Administrators group and authorization profile for this group includes all rights for all available authorization objects. Administrator users can manage ACEN options, add new Programs, Clients, Orders and Licenses and so on.
These are end users (Clients). Clients are granted "Client" role and can access client interface only. Clients can manage their personal data and licenses for their orders.
Client interface is available for standard licensing model only as Client accounts are not required in web licensing model.