Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Clock management
Each team is given three timeouts per half which they can use to stop the clock from running after a play. In the NFL, teams get two timeouts in a preseason or regular season overtime period, or three in a postseason overtime half.