In baseball, the strike zone is the volume of space through which a pitch must pass in order to count as a strike (if the batter does not swing). The strike zone is defined as the volume of space above home plate and between the batter's knees and the midpoint of their torso. Whether a pitch passed through the zone or not is decided by an umpire, who is generally positioned behind the catcher.
Strikes are desirable for the pitcher and the fielding team, as three strikes result in a strikeout. A pitch that misses the strike zone is called a ball. Balls are desirable for the batter and the batting team, as four balls allow the batter to take a base on balls.