(what is twitter by the way?)
Is this a serious question?
If so, Twitter is a service that allows you to post messages of 148 characters or less, with which you can start conversations and interact with people, share links (usually using a small url with bit.ly) etc. It's great for PR and publicity, as well as spreading bare-bones headline news ("bin Laden dead" was all over Twitter a good 3 or 4 hours before the news services started reporting it because some guy on CNN told a friend of his who tweeted it hours before the network's fact checkers were able to confirm the rumor.)