First of all, the clock is a big part of the game. There are four 15-minute quarters and a 30-minute halftime. The teams have 45 seconds to run each play, and the clock stops after every play. So most games take over 3 hours to actually play. You score by running or passing the ball across the goal line. That is called a touchdown, and is worth 6 points. After every touchdown, you can either try a short kick through the goal post uprights for an extra point, or you can try for two extra points by running or passing it across the goal line again on one try. The kick is almost automatic, but ‘going for two’ is much riskier. Many football games are won by just a point or two every season.
The other way you can score is to try a field goal. If a coach doesn’t feel confident that his team can advance any farther down the field, he can elect to just kick it through the uprights from wherever they are instead of trying for a touchdown. A successful kick is called a field goal, and is worth 3 points.
The way a team moves down the field is that you have 4 tries, or downs, to move the ball 10 yards. If you make it past 10 yards in 4 downs, you get another 4 downs. If you don’t make it 10 yards, you have to punt it to the other team, and then you go on defense.
One of the unique things about American football is that the players either play offense or defense, but rarely both ways. There are 11 players on the field on each side, and every player on the field is very specialized in his particular job. They are drafted out of American college teams, there is no minor league or lower level pro teams. The biggest players on the field are the linemen, either offense or defense. Offensive linemen protect the quarterback and block for the runners. They average over 300 pounds these days at the professional level. The defensive linemen try to rush the quarterback to break up his passes, or to stop the runners before they gain any yards. The defensive linemen are still big, maybe 275 or so, but they are fast also. If they tackle the quarterback behind the line of scrimmage, that’s called a quarterback sack, and is a much-coveted statistic for defenders.
Behind the offensive line, the premier player is the quarterback. He runs the offense and is the passer. He also hands the ball off to the runners, who are called halfbacks or fullbacks. The runners are fast and powerful, maybe 210 lbs. or so, but they are getting bigger and faster all the time, as most of the players are. The New York Giants‘ running back, Brandon Jacobs, is 265 and fast. As you can imagine, he’s kind of hard to stop when he gets going. When there is a pass play, the pass receivers are tall, fast and can jump.
On the defensive side, the 3 guys behind the defensive line are called the linebackers, they are about 250. They stop any runners that get past the defensive linemen, but they also have to be fast enough to drop back and cover the fast-running receivers when there is a pass play. Further back are the defensive backs. They are primarily there to break up passing plays. If they can catch a pass thrown by the other team, that is called an interception, and it allows their team to go back on offense.
Another thing that makes the game unique is that the players wear helmets and a lot of protective equipment, which allows the play to be very violent, probably more so than any other sport. The athletes are all extremely strong and muscular, which they need to compete and survive a 16-game season. They are also fast and agile. Even the 300 to 400 pound linemen have quick hands and feet. Hard hitting is encouraged, although there are penalties given for dangerous plays, such as tackling around the neck, head hits, kicking, blocking in the back, and late hits.
American football has evolved over the last 30 years into the premier sport in the USA along with baseball. Football still trails hockey in popularity in Canada. It is played from August through January, leading to the championship game, called the Super Bowl in the USA or the Grey Cup in Canada. American football has never caught on outside North America. Regardless, may North Americans live and die with their teams through the season, and the games have turned into giant media spectacles.
I hope this helps give you some insight into the game. Are you ready for some football?