Google is rolling out video and voice capabilities for the chat function that is embedded in the Gmail interface. It’s simple to install and use.
The first time you use this feature, you’ll be prompted to download and install a small plugin. To get started, visit http://www.gmail.com/videochat or click on the “Options” menu in a Gmail chat window and choose “Add voice/video chat.
PS: Video calls are only available between Gmail chat users with a Gmail voice and video chat plug-in enabled browser.
Voice calls are only available to those using Gmail chat or the Google Talk client.