2.1 Security Principal
A security principal is a common concept in security; it is an actor in a security system and is often something capable of initiating action. Typically, a security principal is associated with a human user of the computer system, but it can also be an autonomous program within the system, such as a logging daemon, system backup program, or something similar.
The security principal is an entity that can be authenticated. In Windows, a security principal is typically a user but can also be a computer or a service. A security principal is often referred to as an account.
Security principals receive permissions to access resources such as files and folders. User rights, such as interactive logons, are granted or denied to accounts directly or via membership in a group. The accumulation of these permissions and rights defines what security principals can and cannot do when working on the network.