Google Talk allows users to send instant messages and make voice calls over the Internet. Its use of the popular XMPP IM standard, used by the Jabber project, allows it to interoperate with chat clients like Apple's iChat, Trillian and the open source Gnome AIM.
For voice calls, the Google developers behind the application plan to support Session Initiation Protocol -- the burgeoning standard for Internet telephony. A number of voice compression algorithms are supported.
For now, only subscribers of Google's Web-based e-mail program Gmail can download Google Talk.
While the Google Talk Web site touts the quality of voice calls using the service, it warns users of its shortcomings. "Google Talk is not a telephony service and cannot be used for emergency dialing," it said.
Google Talk will compete in a crowded Internet telephony market, with rivals such as Microsoft, Yahoo and Skype already offering such services.
The application's advantage may come in what appears to be the initial stages of close integration with Gmail. Google Talk pre-loads a user's Gmail contacts into its database, and lists the user's most frequently e-mailed contacts at the head of the IM column of contacts.
On privacy, the company said: "Google does not collect the content of instant message chats of voice conversations.
"As with all major IM services, Google Talk will collect certain log information created in the course of a conversation."
Google said usage data is later de-identified to prevent abuse. However the company may come under fire for its lack of support for chat and call encryption. "Google Talk currently does not encrypt chats or calls," notes the Web site. "We plan to fully support encryption of chats and calls before our official release."
While the market leader for search has amassed a fortune in advertising revenue with its search engine, Google Talk won't be doing likewise.
"We aren't showing any ads on Google Talk. There are no pop-ups or clutter," the company said.
Google Talk is currently available for systems running Windows 2000 or higher, but plans are afoot to make Macintosh and Linux ports available, in addition to non-English versions.