The World Series is played as a best-of-seven series: Major League Baseball’s American League and National League champions meet, and the first team to win four games is the champion. That means a series can end in four, five, six, or seven games, depending on how quickly one club reaches four wins. According to MLB, the Fall Classic has used the best-of-seven format continuously since 1922 (earlier Series sometimes used best-of-nine), usually in a 2-3-2 home schedule in which one team hosts Games 1–2 and, if needed, 6–7.
Source: MLB.com, “MLB World Series game facts” (Andrew Simon)
Image: 1995 World Series Commissioner’s Trophy (public domain), via Wikimedia Commons.