The Super Bowl, at its most basic level, is a game that determines the NFL championship.
It has become so much more since the first game was played in 1967.
Super Bowl Sunday has become an unofficial holiday in the United States, a day when families and friends gather to watch the game, the over-the-top commercials and big-name musical acts at halftime.
The game and the two weeks of hype, parties and the annual Media Day leading up to it have turned the Super Bowl into a spectacle along the lines of the Olympics or World Cup, a royal wedding or papal celebration, the Oscars or Grammys.
This year's game, between the Seattle Seahawks and New England Patriots, is scheduled Sunday. Here are some reasons why the Super Bowl is so special.
Baseball is known as America's pastime, but football is woven into the country's fabric.
The NFL's rise came at the same time as television's and turned into a $9 billion enterprise. The NFL season has far fewer games than the other major North American sports 16 compared to 162 in baseball which makes every game an event.
But once the season gets to the Super Bowl, many of the fans don't get a chance to go. Tickets started around $800 for this year's game and most are snapped up by corporations.
Cities bid for the right to host the Super Bowl and many use the game as a rallying point to build a new stadium and bring in revenue.
The game is rotated every year, usually to a warm-weather city or one with a domed stadium.
Last year's game was played in the stadium the New York Jets and Giants share in East Rutherford, New Jersey. It was the first outdoor game in a cold-weather city. Future games will be in San Francisco, Houston and Minneapolis.
Arizona's University of Phoenix Stadium, site of this year's game, has a retractable roof and a field that is wheeled outside so the grass can get sunlight.
The Super Bowl is one of the most-watched events in the world, routinely drawing more than 80 million viewers. The game has eclipsed 100 million viewers each of the past five years, with a record 111.5 million watching Seattle roll over Denver a year ago.
Millions more watch the game around the world.
Super Bowl commercials have become a part of the show, luring viewers who might not otherwise watch the game.
The trend of making get-them-talking commercials started in 1984, when Apple created a memorable 1-minute spot based on George Orwell's 1984. Since then, the commercials have included talking animals and babies, supermodels and Clydesdales, sophomoric humor and tear-jerking moments.
The rate for this year's game is $4.5 million for a 30-second spot.
According to the American Gaming Association, Americans will place $3.8 billion in illegal bets on the Super Bowl this year. Nevada Sports Books hauled in a record $19.7 million in legal wagers on last year's game.
The Super Bowl also has some of the most exotic proposition bets anywhere.
For this year's game, bettors can put money on what color Gatorade will be dumped on the winning coach, how long Idina Menzel will take to sing the Star-Spangled Banner, whether Patriots coach Bill Belichick will smile on camera during the game and the color of pop star Katy Perry's hair when she performs during the halftime show.
The halftime show has become must-watch TV instead of just a throw-in with the game.
This year's halftime show will feature Perry and rock guitarist Lenny Kravitz, extending a long line of big-name performers that has included Bruce Springsteen, The Who, Prince, Madonna and Bruno Mars with the Red Hot Chili Peppers last year.
And, of course, everyone remembers Janet Jackson's "wardrobe malfunction" while performing with Justin Timberlake in 2004.
Originally set up for media members to have access to every player on both teams, the annual Media Day has become an event in itself, a spectacle filled with sometimes-wacky questions and attention-grabbing stunts.
In 2008, a reporter from Mexico's TV Azteca wore a wedding dress and asked New England's Tom Brady to marry her. Another Media Day featured a reporter showing up with a puppet of Pittsburgh's Troy Polamalu, calling it his son.
Thousands of media members attend Media Day and fans can buy tickets to watch the festivities for $28.50.
Outside of the Oscars or Grammys, there may not be a bigger place for celebrity parties than the Super Bowl.
The parties before the big game are almost all star-studded and this year's bashes include DirecTv Saturday Night with Rihanna, Nelly performing at Playboy's and Drake at Bootsy Bellows' Pop Up. There also will be live performances in the Phoenix area by Snoop Dogg, Imagine Dragons, Enrique Iglesias with Pitbull and the Zac Brown Band.
Millions of fans also gather in households around the country to watch the game together.
Critical thinking challenge: Why are companies willing to spend so much money for Super Bowl ads?