If you have a microphone on your computer, you can talk to the person on the other end, but there’s no other telephony or VOIP built into Google Talk. AOL Instant Messenger and MSN Messenger already support voice chat, and Yahoo Messenger recently added Internet-based phone calls through its service.
[EDIT 09/03/05] Google Talk requires a Google Gmail account, which is not a completely open program. If you’re not already a Gmail subscriber, you are permitted to sign up for Gmail and Talk if you supply a cell phone number during the signup.
Although the Google service does not feature any unique technical wizardry, it does have one strong point in its favor. AIM, MSN Messenger, and Yahoo Messenger have become bloated with advertising, unwanted “services,” popup pages, and annoying avatars and games and icons and stock tickers and backgrounds and and and . . .
Google Talk’s interface is gloriously, blessedly simple. It sends messages back and forth with no fuss. No ads, no clutter. Also no video or file transfer or group chat, at least not yet.
The various IM services still don’t talk to each other, so make sure you know someone else who will be using the Google service before you get excited about trying it out. Google’s service is built on a slightly more open source that can connect to Apple’s iChat and a handful of others, but AIM, MSN, and Yahoo are still closed services. For what it’s worth, there are rumors that Google will offer a connection to AIM soon.