The object of the game is to score more points than your opponent. When side A has possession they are trying to score points, while side B is trying to prevent them from scoring and trying to regain possession of the ball. There are special teams which come on the field for kickoffs, field goals, extra points and punts. The playing field is 100 yards long and is marked with solid lines every 5 yards.
Goal posts are the odd looking structures located at the back of each end zone.
The ball is now put into play at the point where the runner was downed. This can be done by a player running into the end zone carrying the ball, a player falling on a loose ball in the opponent's end zone, or, by having a player throw the ball to a teammate in the end zone. It's worth 6 points. If successful, it's worth 3 points. There are two methods and the team that scored gets to choose which one to try.