Twitter is a social media platform that allows users to post short messages called tweets that are limited to 140 characters. It launched in 2006 and has over 26.5 million active US users, with growth coming from older adults. Tweets can be posted via mobile, instant messaging, or the web. Users follow other accounts to receive their tweets and can interact by mentioning or retweeting others. The document provides tips on how extension agents can use Twitter to share program updates, advertise events, and engage with clients.