A Windows domain represents both a security and administrative boundary within a Windows network. Computers and users can be added to or removed from a domain. Joining a computer to a domain means that it must abide by certain rules, or policies, that are enforced throughout the domain. It also means that it must give up some of the autonomy that is enjoyed by stand-alone computers by giving over much of the responsibility for determining which users may access it to the domain’s administrator.
Domains consist of three general types of computers running the Microsoft operating systems: