<p>Lightweight Directory Access Protocol (LDAP) is a protocol designed to access directory systems over TCP/IP. Because of this various databases provide an LDAP interface such as <a  href="http://en.wikipedia.org/wiki/Active_Directory" 
        title="enter this page" 
        alt="enter this page" 
        target="_blank"
        rel="nofollow">Microsoft's Active Directory</a>, <a  href="http://en.wikipedia.org/wiki/Novell_eDirectory" 
        title="enter this page" 
        alt="enter this page" 
        target="_blank"
        rel="nofollow">Novell's eDirectory</a>, as well as more dedicated LDAP solutions such as OpenLDAP.
</p>
<p>
Joomla! has had a native LDAP library (<code>joomla.client.ldap</code> (changed to JClientLDAP in Joomla 3.x)) and a native LDAP authentication plugin. This allows Joomla! to authenticate against LDAP systems out of the box: to configure, go to the Plugin Manager and enable and edit the Authentication - LDAP plugin.
</p>

<p>You can also read a <a  href="http://community.joomla.org/component/zine/article/507-developer-ldap-from-scratch-sam-moffatt.html" 
        title="enter this page" 
        alt="enter this page" 
        target="_blank"
        rel="nofollow">tutorial</a> on getting started from scratch with LDAP.</p>

<p><strong>Reference: <a  href="http://docs.joomla.org/Glossary" 
        title="read the reference" 
        alt="read the reference" 
        target="_blank"
        rel="nofollow">http://docs.joomla.org/Glossary</a>
</strong></p>