We have all heard of LDAP and we know how stressful it can be at times. You have to work with paths, username and password and go over an entire list of attributes to find the information you're looking for.
Active Directory is Microsoft service and it's a directory service that uses the LDAP protocol. Many organizations are using it for the ease of use and for the ease of integration with other Microsoft products.
OutSystems supports authentication through both LDAP and Active Directory.
If you have Active Directory configured then go with it instead of using LDAP. It will provide easy access to groups and users (without the use of username / password), manage your directory, import users, groups with detailed information.