The Major League Baseball postseason is an elimination tournament conducted after the regular season, by which MLB determines its World Series champion for a given year.
In this format, for each league, the champions of the East, Central, and West divisions would be joined in the playoffs by a Wild Card team.
The addition of the Wild Card allowed a team that was not a division winner but still had one of the top regular-season records to enter the postseason.
In 2012, the structure was adjusted such that two teams from each league receive Wild Card berths and then play a single game against each other to determine who advances to the Division Series.
And in 2020, after a shortened 60-game regular season due to the COVID-19 pandemic, a special best-of-three Wild Card Series was played; this involved the three division winners, three second-place teams from each division, and two Wild Card teams in each league.