A directory service stores information about resources and provides a way to access this information.
AD provide a consistent way to name, describe, locate, access, manage and secure resources.
Computers and Networks exist to give Users controlled access to resources The goal of Active Directory is to provide a unified view of the corporate network with a reduced number of directories and namespaces. Active Directory uses a DNS-based namespace. DNS and AD are both namespaces. Windows 2000 domain names are DNS domain names, which provide a global naming structure compatible with the Internet. X.509 and Kerberos certificates provide Inter and intra net security.