Active Directory is a Microsoft special directory service. It is a standardized system used by many small and large organizations to centrally manage user authentication. It has a database, which contains all the users and computers information in order to allow users to log on and access network resources. Active Directory enables IT personnel to automate computer security and deploy software to all computers.
This service is provided as a standard service to all university faculty, staff, and students.
More information on Active Directory on Wikipedia http://en.wikipedia.org/wiki/Active_Directory