Relution can be used without any integration of LDAP, ActiveDirectory or Kerberos - only with locally created users and groups.
A LDAP directory as a source of users and/or groups can be used in combination with Kerberos providing single-sign-on to multiple servers/services. On the Windows platform this combination is called Windows Integrated Authentication, the LDAP then is the Active Directory. Notice however, this combination can be used in Unix environments as well. Also, it’s possible to use a LDAP directory for account management only.