The document discusses several popular social networking sites: Facebook, Twitter, and LinkedIn. It provides details on when and how each site was founded, how users create accounts and profiles, and what types of activities can be done on each site. Both advantages and disadvantages of using the social networks are outlined. The key advantages include free communication, connecting with others globally, sharing updates and media, and professional networking opportunities. Disadvantages involve potential addiction, privacy and security risks, wasted time, and learning curves for some sites.