When running with the ball, also known as running. A ball carrier may pass the ball to another player or pass the ball through the air backwards to another player. These are known as a handoff and a side, respectively. Throwing the ball to a teammate, known as a forward pass or passing the ball. The offense can throw the ball forward only once in a play, and only before crossing the line of scrimmage. A down ends and the ball becomes dead after any of the following: The player with the ball is forced to the ground (tackle) or has his advance stopped by members of the other team. A forward pass touches the ground before being caught or out of bounds. This is known as an incomplete pass. The ball is returned to the most recent line of scrimmage for the next down. The ball or football player with the ball extends beyond the dimensions of the field (out of bounds). A team scores. The officials blow the whistle to notify the players that the down is over. Change of Possession – Offense retains possession unless one of the following occurs: The team fails to make a first down (i.e. in four downs they are unable to move ten yards ahead of where they got their last first down descent). The defensive team takes the ball at the point where the fourth down ends. A kicker kicks the ball while his opponent tries to block the kick. The offense scores a touchdown or field goal. The team that scored then kicks the ball to the other team in a special play called a kickoff. The offense kicks the ball to the defense. A punt is a kick where a player drops the ball and kicks it before it hits the ground. Punts are almost always made on a fourth down, when the offensive team does not want to risk giving the ball to the other team at its current spot on the field and feels it is too far from the other team’s goal posts to attempt a goal pitch.