what is jabber?
Jabber is a free, open, XML-based protocol for real time message exchange. It is similar to legacy instant messaging systems such as ICQ and MSN but is open, extensible and decentralised. The fact that it is decentralised means that anyone can run their own Jabber server using one of the many available Jabber servers.
The Jabber protocol (XMPP Core) was approved as a standard by the Internet Engineering Task Force in early 2004.
You can find a technical overview of Jabber here
