Twitter is a social media platform launched in 2006 that allows users to post and read text-based messages known as tweets that are limited to 140 characters. It has over 340 million active users who can follow other users and have their tweets seen by their followers. Some key facts are that Twitter was originally intended as an "SMS of the Internet" and was created by Jack Dorsey, and it now sees over 340 million tweets posted per day making it one of the top 10 most visited websites.