Twitter is a free social network. It provides its users with an easy way to always stay connected with their friends, family and co-workers. This is enabled by posting updates on the site, instant messaging (e.g. SMS, RRS), short messaging, and third party applications (e.g. Twitterrific).
Once an update is posted it appears on the users profile page and is delivered to all users signed up to receive them. Although the default is delivery to all users, the user can limit it to their friends.
Many organizations and Higher education institutions love using Twitter and find it very efficient in locating employees in cases of emergencies and to pass on important information in manner that better suites the modern way of life.