Twitter is an American-based social networking site, which allows users to interact through short messages known as “tweets”. Tweets were originally limited to 140 characters, but that restriction has since increased to 280 characters. The site was created by tech entrepreneurs Jack Dorsey, Evan Williams, Noah Glass and Biz Stone in 2006, and is currently one of the most-visited sites on the internet. The headquarters for Twitter, Inc. is located in San Francisco, CA.