Google Talk enables you to call or send instant messages to your friends for free anytime, anywhere in the world. Google Talk (GTalk) is a Windows and web based application based on VOIP and instant messaging format.
Instant messaging between the Google Talk servers and its clients uses an open protocol, XMPP, which allows users of other XMPP clients to communicate with Google Talk users. VoIP in Google Talk is based around the Jingle protocol.
Here are some key features of Google Talk:
• Choice: Get in touch how and when you want to over email, IM or a call
• Quality: Talk through your computer but hear your friends as if they were in the same room
• Convenience: Your Gmail contacts are pre-loaded into Google Talk so inviting or talking to your friends is just a click away