Twitter is a microblogging platform that allows users to post short updates called tweets. Tweets are limited to 140 characters and can include hashtags, which are keywords preceded by a # symbol that link to other tweets on the same topic. Hashtags help people find tweets about trending topics and allow information to spread in real-time. However, campaigns using vague hashtags can be hijacked, as seen when McDonald's #McDstories was used to criticize the company.