With ADSI, Microsoft hopes to extend directory look-ups and searches to the desktop programmer. Well, as I mentioned before, user account and validation information plus much more. All Windows NT 5.0 domain names are now DNS domain names. Included with this are the zone or hierarchical DNS names. In fact, Microsoft has included the recent Dynamic DNS protocol, which allows remote administration of DNS name spaces.
Security is a big issue too.
NT systems, but uses Kerberos v5.0 by default for authentication, data integrity, and data privacy. Kerberos is faster than NTLM, so users log on quicker. And Kerberos has the ability to delegate authentication. Delegation allows Active Directory to clean up a problem that has plagued NT administrators who maintain multiple NT domains in their organizations. Before NT 5.0, administrators could grant access to one domain user for resources under another domain by establishing a Trust between the two domains.