Twitter

Twitter is a social networking and micro-blogging service that allows users to send "updates" (text-based posts, up to 140 characters long) via SMS, instant messaging, email, the Twitter website, or an application such as Twitterrific. Twitter was founded in March 2006 by San Francisco start-up company Obvious Corp.

Updates are displayed on the user's profile page and also instantly delivered to other users who have signed up to receive them. The sender can restrict delivery to those in his or her circle of friends (delivery to everyone is the default). Users can receive updates via the Twitter website, instant messaging, SMS, RSS, email or through an application. For SMS, currently three gateway numbers are available: short codes for the USA and Canada and a UK number for international use. While the Twitter service is free, posting and receiving updates via SMS may incur charges from the wireless carrier. Several third parties offer posting and receiving updates via email.