Twitter is a social media platform that allows users to share messages called tweets that are limited to 140 characters. Users can follow other accounts and see their tweets on their homepage. Popular features include hashtags to discuss topics and retweeting others' tweets to share with one's own followers. Marketers use Twitter for brand recognition, content promotion, direct communication with customers, and increasing sales. Effective use involves following others, posting engaging content using hashtags, and interacting with one's audience.