Authorization
Authorization is the process of answering the question "What are you allowed to do?". It is the process of determining whether a user or system has the necessary permissions to access a resource or perform a specific action. Authorization process starts after the authentication process. Once the user or system is authenticated, the authorization process determines what actions the user or system is allowed to perform.
Authorization may be a very complex process. In order to make everthing more clear, lets begin by defining some fundamental terms.