It's a simple little thing that allows a kind of nano-blogging; you can use your phone or your computer to announce (to your friends or to the world) what you're doing right now.
And some people do that. Others use it as a platform for jokes or complaints, or to announce the biscuits they're going to eat in a meeting. For some, it's a digital postcard. Most people use it as a virtual equivalent of the quick "hello" in the corridor.
It's stupid, pointless, trivial and completely addictive. The best introduction is to go to twittervision.com and watch the twitters roll in from around the world: it's like a haiku-sized soap opera with a cast of digerati grouching and joking through their digitally mediated lives. I mention it because Twitter points at some interesting things to think about:
1. It wasn't invented by who it should have been invented by.
Twitter has driven massive amounts of increased text usage, from me alone, yet it wasn't invented by any telco, it was invented by some software/web guys in Silicon Valley, because it was a service they wanted. The costs of developing these things are so low now, that ideas such as this are popping up everywhere, in a fraction of the time it would take to squeeze them through a corporate hierarchy. And it didn't have to be tech guys. It could have been someone reading this.
2. The stuff we used to dig for is now bubbling to the surface.
If I was launching a global marketing campaign today, especially if it was vaguely techy, I'd project a big Twittervision screen on the wall and see if it showed up there. That would be a sign of success. I bet Apple could do that - watching the twitterings about the iPhone announcement was a mark of their brand power. You can see your campaigns unfold on blogs today, but it's slow, it doesn't really live up to the name "buzz". When/if Twitter gets big, you'll know immediately if you've made an impression.
3. You won't understand it until you try it.
It's become increasingly clear to me that you can't explain new media to people. Just as you can't understand TV by reading about it, you can't really get digital media without trying it. It's not how the service works that's important, it's how it feels to do it and share it with your friends. So have a go. And add me at twitter.com/russelldavies.