The LDAP is a directory service protocol that runs directly over the TCP/IP stack, and provides a mechanism for connecting to, searching, and modifying Internet directories.
The LDAP directory service is based on a client-server model. The function of LDAP is to allow access to an existing directory. Microsoft® Exchange 2000 Server messaging and collaboration application clients can use LDAP to access user and group information across a network or the Internet.
More information about LDAP is available from the MSDN® Lightweight Directory Access Protocol API Web site.