Google Talk, offered and developed by Google Inc, is a free Windows web-based application for instant messaging and
Voice over Internet Protocol (VoIP)
that uses an open protocol, XMPP, allowing users of other XMPP/Jabber clients to communicate with Google Talk users. VoIP in Google Talk uses an older version of what would later become the Jingle protocol. Some of other features of this software is Voicemail, file-sharing and offline messaging.
The Latest Version.
The most recent version of the program is Google Talk 1
that is only available for Microsoft Windows (2000, XP, Server 2003, Vista and Windows 7), but Google Chat (voice and video chat) is now available for PCs and Intel-based Macs.