LDAP attributes are used when setting up claim rules in AD FS.

Using LDAP attributes one can easily extract AD attributes for an authenticated user from the AD attribute store thereby providing the required claims for each/all Relying Party setup in AD FS. LDAP attributes are not case sensitive, but used here for readability.

LDAP: The Lightweight Directory Access Protocol is an open industry standard used for accessing and maintaining distributed directory information such as Microsoft Active Directory.