Short answers, pulled from the story.
A wild card is an invitation to a tournament or a playoff berth awarded to a team or individual that did not qualify through an automatic bid, such as winning a division or conference. Some events allow organizers to grant them freely; others follow fixed rules based on records.
Seven NFL wild card teams have won the Super Bowl: the 1980 Oakland Raiders (Super Bowl XV), the 1997 Denver Broncos (Super Bowl XXXII), the 2000 Baltimore Ravens (Super Bowl XXXV), the 2005 Pittsburgh Steelers (Super Bowl XL), the 2007 New York Giants (Super Bowl XLII), the 2010 Green Bay Packers (Super Bowl XLV), and the 2020 Tampa Bay Buccaneers (Super Bowl LV).
MLB instituted the wild card in 1994, but implemented it for the first time in 1995 after both leagues reorganized into three divisions each. The system has been expanded twice since then, most recently adding a third wild card per league and replacing the single play-in game with two three-game wild card series.
Goran Ivanisevic won the 2001 Wimbledon Men's Singles championship after the All England Lawn Tennis and Croquet Club granted him a wild card entry. At the time he was ranked world No. 125 due to a shoulder injury, though he had previously reached the Wimbledon final three times.
The NFL was the first sports league to use the wild card format, introducing it in 1970 following the completion of the AFL-NFL merger. The qualifying team was initially called the "Best Second-Place Team" or "Fourth Qualifier" before the media began using the term "wild card," which the NFL eventually adopted officially.
Eight wild card teams have won the World Series: the 1997 Florida Marlins, the 2002 Anaheim Angels, the 2003 Florida Marlins, the 2004 Boston Red Sox, the 2011 St. Louis Cardinals, the 2014 San Francisco Giants, the 2019 Washington Nationals, and the 2023 Texas Rangers.