 American football , referred to as football in the United States and Canada , and also known as gridiron , is a sport played by two teams of eleven players on a rectangular field with goalposts at each end . The offense , the team with control of the oval @-@ shaped football , attempts to advance down the field by running with or passing the ball, while the defense tries to stop their progress. nobody is allowed to run with the ball except the players on offense. Points are primarily scored by advancing the ball into the opposing team’s end zone for a touchdown or kicking the ball through the ball’s vicinity.