The document provides an overview of Twitter, including:
1. Twitter allows users to post short "tweets" of up to 140 characters to share updates and follow discussions from other users.
2. It launched in 2006 and has grown significantly since then, with over 10% of internet users estimated to have Twitter accounts in 2009.
3. Key aspects of Twitter include tweets, retweets, hashtags, following other users, and direct messages. The document also provides tips on using Twitter effectively.