Yesterday at its f8 developer conference, Facebook engineers Ruchi Sanghvi and Ari Steinberg gave what may be the first thorough walkthrough of the underpinnings of Facebook News Feed, the all-important page that users see when they first log on to the site. After giving an overview of the history of News Feed, which has evolved quite a bit since it launched in 2006, they offered some insight into the algorithms that allow News Feed to show you relevant content, collectively called EdgeRank.

You may not realize it, but News Feed only displays a subset of the stories generated by your friends — if it displayed everything, there’s a good chance you’d be overwhelmed. Developers are always trying to make sure their sites and apps are publishing stories that make the cut, which has led to the concept of “News Feed Optimization”, and their success is dictated by EdgeRank.