Facebook Graph Search is Facebook's internal search engine that utilizes user profile and connection data to return relevant search results. The document discusses how Graph Search works currently, focusing on searches for restaurants, movies, and places recommended by friends. It also speculates how Graph Search may evolve to include more customized content from brands and how content, profiles, and the value of user actions like "Likes" could impact search rankings. Each user's authority and the quality of their connections and engaged fan bases may determine how much their actions influence search results.