In team sports in the U.S. and Canada, the vast distances and consequent burdens on cross-country travel have led to regional divisions of teams. Generally, during the regular season, teams play more games in their division than outside it, but the league's best teams might not play against each other in the regular season. Therefore, in the postseason a playoff series is organized. Any group-winning team is eligible to participate, and as playoffs became more popular they were expanded to include second- or even lower-placed teams – the term "wild card" refers to these teams.
In England and Scotland, playoffs are used in association football to decide promotion for lower-finishing teams, rather than to decide a champion in the way they are used in North America. In the EFL Championship (the second tier of English football), teams finishing 3rd to 6th after the regular season compete to decide the final promotion spot to the Premier League.
Evidence of playoffs in professional football dates to at least 1919, when the "New York Pro Championship" was held in Western New York (it is possible one was held in 1917, but that is not known for sure). The Buffalo and Rochester metropolitan areas each played a championship game, the winners of which would advance to the "New York Pro Championship" on Thanksgiving weekend. The top New York teams were eventually absorbed into the NFL upon its founding in 1920, but the league (mostly driven by an Ohio League that did not have true championship games, though they frequently scheduled de facto championship matchups) did not adopt the New York league's playoff format, opting for a championship based on regular season record for its first twelve seasons; as a result, four of the first six "championships" were disputed. Technically, a vote of league owners was all that was required to win a title, but the owners had a gentlemen's agreement to pledge votes based on a score (wins divided by the sum of wins and losses, with a few tiebreakers). When two teams tied at the top of the standings in 1932, an impromptu playoff game was scheduled to settle the tie.
The National Football League divided its teams into divisions in 1933 and began holding a single playoff championship game between division winners. In 1950 the NFL absorbed three teams from the rival All-America Football Conference, and the former "Divisions" were now called "Conferences", echoing the college use of that term. In 1967, the NFL expanded and created four divisions under the two conferences, which led to the institution of a larger playoff tournament. After the AFL-NFL merger brought the American Football League into the NFL, the NFL began to use three divisions and a single wild card team in each conference for its playoffs, in order to produce eight contenders out of six divisions; this was later expanded in 1978 & 1990 so that more wild card teams could participate.
In 2002 the NFL added its 32nd team, the Houston Texans, and significantly reshuffled its divisional alignment. The league went from 6 division winners and 6 wild card spots to 8 division winners and only 4 wild card qualifiers. The winners of each division automatically earn a playoff spot and a home game in their first rounds, and the two top non-division winners from each conference will also make the playoffs as wild-card teams. The top two teams with the best records in the regular season get a first round bye, and each of the bottom two division winners plays one of the two wild-card teams. Each winner of a wild-card game then plays one of the two bye teams. The winners of these two games go to the conference championships, and the winners of those conference championship games then face each other in the Super Bowl.