LDAP (Lightweight Directory Access Protocol) enables you to use a single authentication authority for different applications. For instance, your company might already have an Active Directory installation with LDAP enabled. In this case, rather than having to maintain all of your company's user IDs and passwords separately within mojoPortal, you can instead enable LDAP in mojoPortal and use your LDAP server to authenticate and log users into both the Windows domain and mojoPortal site(s) using the same Windows username and password.
As of mojoPortal version 220.127.116.11 and higher, there is an additional method of authentication: Database authentication, with fallback to LDAP if database authentication fails. This will allow you to use LDAP authentication for your internal users, but still allow outside users (who do not exist in LDAP) to register and log into your site(s) with database authentication. For more on this option, see the Using Active Directory or Using OpenLDAP pages.
Edited 2012-12-11 Jamie Eubanks