The document provides information on top social media sites including their category, description, when to use them, Alexa rank, and year since founded. Some of the key sites mentioned include Facebook (social networking), YouTube (video sharing), Twitter (microblogging), LinkedIn (professional networking), Pinterest (visual discovery), Instagram (photo sharing), and Google+ (social networking). The document serves as a useful reference for the most popular social media platforms and when each one might be best used.