The college basketball "madness" march begins Tuesday with first-round elimination games in the NCAA men's basketball tournament -- a three-week ritual that's marking its 75th anniversary. So get set for a basketball binge that that fills social media, screens of all sizes, conversations and arenas in each region of America. Off the court, the tournament is a big business, generating more than 95 percent of the NCAA's revenue from broadcast rights, a share of ticket fees, sponsorships and merchandise sales.

Thirty-one Division I teams qualified for the tournament by winning their conference titles. A NCAA committee Sunday night announced at-large selections for 37 other teams. Excitement flows from rooting for local or home state teams, or schools attended by friends or family members. Interest also is generated by the live-action drama of underdog triumphs and long-shot victories at the final buzzer. With 33 games, a David-beats-Goliath surprise happens most years.

It all culminates with Final Four semifinal and final games April 6 and 8 at the Georgia Dome in Atlanta. The NCAA women's tournament, with selections announced Monday, runs through an April 7 and 9 championship series in New Orleans. As part of 75th anniversary year events, fans can vote online (www.ncaa.com/MarchMadness) through March 24 for the best team, most memorable moment and best players. The final results — the top 15 players, along with the top team and most memorable moment — will be revealed April 5. The final selections will be honored the next day in Atlanta during the semifinal games of the men's tournament.

Blogger says: "An amazing aspect of the tournament is the upsets that catch everyone off-guard and shock the sport. Nothing feels quite like watching a No. 1 seed lose in the first round." – Donald Wood, BleacherReport.com columnist

What are brackets? The NCAA pairs teams against each other in the tournament's opening rounds based on their records this season and other factors. Those pairings, displayed on a chart printed and posted by newspapers, are known as brackets. This year's were announced Sunday, and even President Obama will fill one out in an attempt to predict winners.

Best player voting: 75 former college legends are on the 75th anniversary online ballot, which includes Kareem Abdul-Jabbar, Wilt Chamberlain, Patrick Ewing, Jordan, Bill Russell, Isiah Thomas and Bill Walton.