Google Talk is an XMPP [L1 ] (aka. Jabber) based Instant Messaging IM application that is tied in with Google's e-mail handling service Google Mail. Google provide a client that can do the usual IM activities (messaging, chat and group chat) and also does voice and video links using their Jingle extension [L2 ] to the XMPP protocols.
As XMPP is an open RFC derived from Jabber and Google have hooked their servers into the J