What is it?

Tor Messenger is a cross-platform chat program that aims to be secure by default and sends all of its traffic over Tor. It supports a wide variety of transport networks, including Jabber (XMPP), IRC, Google Talk, Facebook Chat, Twitter, Yahoo, and others; enablesOff-the-Record (OTR) Messaging automatically; and has an easy-to-use graphical user interface localized into multiple languages.

Source: Tor Messenger Beta: Chat over Tor, Easily | The Tor Blog