Twitter is a free micro-blogging tool that allows users to publish short messages (140 characters or less) through their computers and mobile phones. Twitter launched in 2007 and nearly 1 million people were using it within one year of its debut.

People who use Twitter write short messages, called Tweets, which they publish either publicly (for all Twitterers to see) or privately (for only certain Twitterers to see).

Typically, users will sign up to follow other users whose Tweets they enjoy. For this reason, Twitter can be a great tool for networking, relationship-building and promoting blogs.

Businesses also use Twitter to promote products and services and offer real-time customer service. Twitter provides an excellent source of free publicity.