Jabber

Jabber is an open-source instant messaging protocol. LJ Talk uses the Jabber protocol to send and receive data. Other notable implementations of Jabber include Google Talk.

Unlike closed and proprietary services like AIM, Yahoo!, and MSN, anyone can run a Jabber server on their own domain. If a Jabber server is federated, it can talk with other federated Jabber servers. Some hosts, like Dreamhost, even include Jabber service with their web hosting plans. Because LJ Talk is federated, users will be able to talk with other Jabber services like Google Talk.

Links

 * Wikipedia article on Jabber