Access Control System, An access control system is a system which enables an authority to control access to areas and resources in a given physical facility or computer-based information system.
Authentication - Process of providing the identity of a user. (Who are you?)
Authorization - Process of granting or denying access rights for a resource to an authenticated user. (What are you allowed to do?)
Credentials - Information that includes identification and proof of identification that is used to gain access to resources. Examples of credentials are user names and passwords, smart cards, and certificates.