Social media are online platforms that allow users to interact, connect and share content. Twitter is a microblogging service that allows users to post messages of up to 140 characters. While Twitter started as a personal platform, many businesses now use it for branding, marketing and customer service. The document provides examples of how companies like Virgin Trains and Domino's Pizza have used Twitter successfully in customer relations and crisis management. It also outlines best practices for businesses to engage customers on Twitter through transparency, honesty and authenticity.