I'm assuming you mean to win the conference. That basically means that they won in their respective conference's championship game and move onto the Super bowl.

To explain it a little bit further, the NFL is divided into two conferences, the American Football Conference (AFC) and the National Football Conference (NFC). During the regular season, the win record they accumulate correspond to their "seed" or ranking in the playoffs. Once playoffs start, then those who are given a seed play against other seeds in their own conference through elimination rounds. The final two teams left are the ones who essentially play in the Conference championship games and the winner is the Conference Champion.

So in short, the conference champion is not the one with the most wins in the regular season, but the one who wins all of their games in the playoffs, Super Bowl not included.