Most people I know on Facebook have moved to Twitter but I don't know why? What's the big deal with Twitter?
It's a kind of social networking site, and is generating huge amounts of buzz among the web's early adopters thanks to a simple conceit. All twitter.com does is ask: "What are you doing?"
The idea is that it offers a way for individuals to provide more detailed status updates to their friends, family and contacts. And, crucially, it delivers those updates across a variety of different media – either through its website, over instant messaging or by SMS to your mobile phone.
Twitter's service is the logical evolution of blogging. The two platforms have much in common; and while blogging is still much derided, it has been adopted by millions of people.
http://www.obsessable.com/feature/what-is-twitter/