power rankings

http://www.realsport101.com/nfl-power-rankings-week-14-sees-huge-number-changes-rankings/ - Big changes in the Power Rankings this week. Good to see us moving up the rankings!

http://www.realsport101.com/nfl-power-rankings-wild-card-chasers-rise-as-new-england-fall-out-of-top-3-after-week-13/ - anyone got an easy to understand explanation for a UK based NFL fan as to how Power Rankings actually works? Is it an imparital thing? or is there a genuine scale?