The National Collegiate Athletic Association Men's Division I Basketball Tournament, commonly known as March Madness, is an annual tournament for college basketball teams that determines the national champion. It starts with 68 teams, and the winner of each game advances to the next round while the loser is eliminated.
The tournament progresses rapidly over the course of a few weeks in the month of March, hence the name March Madness. About half of the teams earn their place in the tournament by winning Division I conferences. The National Collegiate Athletic Association chooses the other teams. It ranks teams by performance and determines which teams play each other in the first-round games based on these rankings. Teams in the tournament come from four U.S. regions: the Midwest, the West, the South and the East. For most of the tournament, teams play other teams from the same region. The winning teams from each of the four regions, known as the Final Four, play each other in the final three games of the tournament to determine the national champion. Many college basketball fans participate in March Madness by filling out brackets to predict the winners of all the games in the tournament. An identical Women's Division I Basketball tournament takes place at the same time as the Men's tournament but is not as popular or widely broadcast as the Men's tournament.