Role-based access control - Wikipedia
"In computer systems security, role-based access control (RBAC) or role-based security is an approach to restricting system access to authorized users. It is used by the majority of enterprises with more than 500 employees, and can implement mandatory access control (MAC) or discretionary access control (DAC).
Role-based access control (RBAC) is a policy-neutral access-control mechanism defined around roles and privileges. The components of RBAC such as role-permissions, user-role and role-role relationships make it simple to perform user assignments. A study by NIST has demonstrated that RBAC addresses many needs of commercial and government organizations"
Role Based Access Control | CSRC @ NIST
Role-Based Access Controls (PDF, original paper describing the concept)