Authentication and authorization are often confused with each other.
Authentication is the process of securely identifying a user based on credentials presented (username, password, security token, etc.) For website user authentication, Georgia Tech predominantly uses Central Authentication Service (CAS), often times referred to as the GT Login Service.
Authorization is the process of determining what roles and/or privileges an authenticated user has been granted. For user authorization, there are options available through both CAS SAML attributes and through LDAP queries.