This is a term used in sports, such as football, defined as the
games played in the post-season to determine who the season's
champion is. After the regular season has concluded, the best teams
move on to the playoffs.
In the National Football League, the playoffs are four rounds, with the final round being the Super Bowl, the championship game. Each conference sends six teams to the playoffs; four division winners and two wild-card teams. The wild-card teams are the top two teams in the conference, based on win-loss records, who did not win their division. The first round, also known as the wild-card round, has eight teams and pits each of the wild card teams against a division winner. The conference winner gets a bye in the first round. The second round, known as the divisional round, pits the winners against each other, while also introducing the conference winner into the mix. The third round is the conference championships, which pits the winners of the previous round against each other. The final round, the Super Bowl, pits the final two winners against each other to determine the champion.
In the second round of the playoffs, the conference winner is
plays either the worst division leader or one of the wild card
teams. This gives the conference winner the advantage of playing,
presumably, the worst teams still in the playoffs. The conference
winner also has home-field advantage throughout the playoffs. The
system currently in place has been the rule since 2002, and only
changed by removing a wild card team from the mix (there were
formerly three wild card teams).
There are also many tie-breaking rules which may be used in cases where win-loss records are identical. This is important for deciding who plays whom and where the game takes place.