As of 2015, Major League Baseball consists of 30 pro teams. Fifteen teams compete in both the American League and National League, with the winner of each playing for the World Series.
Within each league are geographically aligned East, Central and West Divisions comprised of five teams each. The three division winners clinch postseason berths, while the fourth- and fifth-best AL and NL teams compete in a one-game playoff to determine who plays the division champion with the best overall record in the next round, the best-of-five Division Series. The two Division Series winners in each league then compete in the best-of-seven Championship Series, with the winner advancing to the World Series.