Assuming you want American football, also called gridiron football:
The basic rules of American football are simple. Two teams of 11 players each take turns trying to move the ball down the field and score points by either carrying it into the end zone or kicking it through the goal posts. The team with the most points at the end of the game wins.
The offense, which is the team with the ball, has four downs, or chances, to gain 10 yards and keep possession of the ball. If they don’t make 10 yards after four downs, then they have to turn over possession of the ball to their opponent, unless they kick a field goal on fourth down. A touchdown is worth six points and a field goal is worth three points. After scoring a touchdown or field goals, teams can attempt an extra point by kicking the ball through goal post from scrimmage (worth one point) or running or passing it into end zone (worth two points). Safeties are worth two points for defensive team and usually occur when offensive team gets tackled behind its own goal line.
Each game is 60 minutes long divided into four quarters. At halftime there is a break of about 15 minutes. Between quarters there is a break of 2 minutes for television commercials except during NFL playoffs when games cannot be interrupted for commercials. During NFL playoffs games are only 3 hours long without commercial breaks between quarters.