In Windows 2000, a domain defines both an administrative boundary and a security boundary for a COLLECTION of objects that are relevant to a specific GROUP of users on a network. A domain is an administrative boundary because administrative privileges do not extend to other domains. It is a security boundary because each domain has a security policy that extends to all security accounts within the domain. Active Directory stores information about objects in ONE or more domains.
Domains can be organized into parent-child RELATIONSHIPS to form a hierarchy. A parent domain is the domain directly superior in the hierarchy to one or more SUBORDINATE, or child, domains. A child domain also can be the parent of one or more child domains.

In Windows 2000, a domain defines both an administrative boundary and a security boundary for a collection of objects that are relevant to a specific group of users on a network. A domain is an administrative boundary because administrative privileges do not extend to other domains. It is a security boundary because each domain has a security policy that extends to all security accounts within the domain. Active Directory stores information about objects in one or more domains.
Domains can be organized into parent-child relationships to form a hierarchy. A parent domain is the domain directly superior in the hierarchy to one or more subordinate, or child, domains. A child domain also can be the parent of one or more child domains.