A major (maybe the most important) feature introduced with Windows 2000 is Active Directory. Active Directory is a directory service that provides a central, hierarchical store for user information, network resources, services, and so on. It is also possible to extend the information in this directory service in order to store custom data that is of interest for the enterprise.
For example, Microsoft Exchange Server 2003 and Microsoft CRM use Active Directory intensively to store public folders and other items.
Before the release of Active Directory, Exchange Server used its own private store for its objects. It was necessary for a system administrator to configure two user IDs for a single person: a user account in the Windows NT domain to enable a logon, and a user in Exchange Directory. This was necessary for the additional information required by users (such as e-mail addresses, phone numbers, and so on), and the user information for the NT domain was not extensible to add the required information. Now the system administrator just has to configure a single user for a person in Active Directory; the information for a
user object can be extended so that it fits the requirements of Exchange Server. You can also extend this information.
If you require the user information to be extended with a skills list, storing user information in the Active Directory makes this possible. Here it would easily be possible to track down a C# developer by ...