Jabber is a protocol, and the data it tranfers is formatted with XML. Its number one application is instant messaging, and in fact was created specifically for that. But it can do all kinds of other cool things too.
The thing that sets Jabber apart from other instant messaging services is that there isn’t a single centralized server, like with AIM, YIM, and MSNIM. Anyone can set up a server, and it can talk to other servers. It’s VERY similar to email in that regard. When I send a message, it goes from my computer to my server to your server to your computer.
Several months ago, Google announced its new IM service, called Google Talk. It could do text and voice communication. What most people don’t know is that it’s pretty much just a giant jabber server. That’s very cool for the technology, but the big crippling blow was that it couldn’t talk to other jabber servers. This made it little different from any of the other big IM services. Deep in my heart though, I knew Google would do the right thing.
And today they did. They opened up Google Talk to talk to other jabber servers. The voice stuff will continue to only work in their client (until Sean gets it working in gaim; Go Sean!), but it opens up a huge new group of existing users.
Google also recently bought a small bit of AOL, and there are strong (probably true) rumors that Google Talk will soon also be able to interact with AIM.
Jabber may have just become serious.