NFL Tiebreaking procedures?

It means the best win/loss record against common opponents outside of the division. For example if you look at the schedule for a division for the season you will notice that they schedule games twice per season against their division, and then they schedule each team to play an AFC division and an NFC division. This season the AFC west plays each team in the AFC east and NFC south. If there is a tie in the AFC west, then the third tie-breaker would be how each team fared against those AFC east and NFC south opponents.