A 2004 article from SearchWindowsServer.com but still applies. by James Michael Stewart, Contributor

One or more group policies (GPOs) can be defined for each domain, site, and organizational unit (OUs) in a forest (that is, an entire Active Directory domain network). All of the GPOs can be managed from a Windows 2000 or Server 2003 domain controller system through the Active Directory Users and Computers utility as well as several others.