American football is a really awesome sport. With 32 different teams in regions all over the USA, It is America's most popular spectator sport.
There are 2 conferences in the NFL, Each with 4 divisions. Every division has 4 teams.
In a game of American Football, there can only be 22 players on field. 11 for the offense and 11 for the defense. There are also many positions in the game.
Here are some offensive positions: QB (Quarterback), WR (Wide Reciever), RB (Running Back), OT (Offensive Tackle).
Here are some defensive positions: DE (Defensive End), DT (Defensive Tackle), CB (CornerBack), LB (Linebacker).
There are many rules, but here are some of them: Rule Book Link
You play the game by trying to score points. You score points by trowing the ball to a teammate in the touchdown, or by running into the touchdown with the ball ,or by kicking a field goal. That is when you are on offense. When you are on defense you want to try to stop them from scoring. You do that by intercepting a ball (when the QB throws it), or by causing a fumble (hitting the ball out of someone's hand), or by causing a loss of downs (when they don't get to the 1st down line before 4 downs are over.)