Habitual users of a new, free communications service called Twitter would disagree. For anyone unfamiliar with the latest trends in technology, "Twitterers" send and receive short messages, called "tweets," on Twitter's Web site, with instant messaging software, or with mobile phones. Unlike most text messages, tweets - usually in answer to Twitter's prompt, "What are you doing?" - are routed among networks of friends. Strangers, called "followers," can also choose to receive the tweets of people they find interesting.
Link: Twitter Web Page