The term domain can refer either to a local subnetwork or to descriptors for sites on the Internet (e.g., www.uwstout.edu).  On the Internet, a domain is part of every network address, including website addresses, email addresses, and addresses for other Internet protocols.

A domain is a sub network made up of a group of clients and servers under the control of one central security database. Within a domain, users authenticate once to a centralized server known as a domain controller, rather than repeatedly authenticating to individual servers and services. Individual servers and services accept the user based on the approval of the domain controller.