Facebook is a social network that connects users with people around them through an online network organized by location and interests. Users can add friends, send messages, and update their profiles. They can see their friends' profiles and updates. Twitter is a free service that allows users to post short messages of 140 characters or less called tweets. Users can follow other users to see their tweets and engage with others by replying, retweeting, or direct messaging them. Twitter provides a simple way to connect and share with others online.