Your server can be in a workgroup, active directory environment, or Windows NT 4 domain. In Microsoft Windows NT 4 and Microsoft Active Directory environments, a domain is a collection of computers defined by the administrator of a network that share a common directory database.
Utilized for Windows user and group information, Windows domains have a unique name and provide access to the centralized user accounts and group accounts maintained by the domain administrator. Each domain has its own security policies and security relationships with other domains, and each domain represents a single security boundary of a Windows computer network. Active Directory is made up of one or more domains, each of which can span more than one physical location.
For DNS, a domain is any tree or subtree within the DNS name space. Although the names for DNS domains often correspond to Active Directory domains, DNS domains should not be confused with Microsoft Windows and Active Directory networking domains.
By default a domain user must enter domain\username when logging into a Web server or a NAS with a Netscape browser.
To set the default domain used for logon