A right handed batter standing ready at home plate.  The imaginary rectangle in front of the batter is the "strike zone".

Mickey Mantle of the Yankees batting left handed.  The catcher of the defense team squats behind the batter, and the umpire, who calls the balls and strikes, is behind the catcher.

The classic baseball confrontation: the pitcher vs. the batter.  Pitched ball heads in towards the strike zone, the batter swings, and the ball is either hit or missed.  The catcher and umpire are behind the batter.
 

When the pitcher pitches the ball, and the ball touches or goes through this imaginary area, and the batter does not swing at the ball with his bat or swings and completely misses the ball, i.e. makes no contact of the bat on the ball, this act is called a "strike".  The batter is entitled to 3 strikes before he is called "out".  If the batter has less than 2 strikes against him, and he swings the bat and makes contact with the ball, but the ball hits the ground in the foul area without a defense team player catching the ball, this is also considered a strike against the batter.  If the batter already has 2 strikes against him, further hits into the foul area are not considered strikes.  Once a batter has a 3rd strike, either from not swinging at a ball thrown into the strikezone or swinging but missing contact with the ball, the batter is considered "out".

A ball pitched by the pitcher which is not in the strike zone, and the batter does not swing at the ball, known as the batter "holding his swing", this ball is considered a "ball".  Anything not a strike is a ball.  If the batter can achieve 4 balls before the 3rd strike and before hitting the ball into the fair play area, the batter will cease batting, and can advance to first base.  This is called a "walk".  At any time, if the pitcher pitches a ball which touches any part of the batter or his uniform, the batter is automatically given a "walk".  The batter, however, doesn't want to get hit by a pitcher ball, because a hard object, which the ball is, travelling at a high speed of 90 miles (150 kilometers) per hour, when striking any part of the batter's body, will hurt.

Pitchers try to throw pitches that are difficult for the batter to hit, by using speed and other motions to cause the ball to move in unpredictable fashion as it travels from the pitcher's hand past the batter to the catcher squatting behind the batter. The umpire, in black outfit, is the one who decides whether the thrown pitch is a strike or ball, when the batter does not swing at the pitched ball.

The combination of balls and strikes against each batter is known as "the count". For example, if the count on a batter is 2 and 1, this means this batter has 2 balls and 1 strike against him.  When the count reaches 3 and 2, this is known as a "full count", because it is possible that the next pitched ball will enable the batter to walk to first base on 4 balls, or the batter will strike out on 3 strikes.

An "out" is a number that determines when the offense team ceases to be on offense, and switches to defense.  Once the offense team has 3 outs against it, it ceases its offense, and takes the field to play defense, and the team that had been on defense comes off the field to become the offense team.  In each inning, each team plays offense once, and defense once.  In Major League Baseball, it is normal that neither team can score any runs in most innings.  It is difficult to score a run given the excellent ability of the defense team to prevent runs scored against it.

An out can be made against the offense team when any batter strikes out, a batted ball is caught in the air before it touches the ground or any part of the stadium, the batter has hit the ball into the fair play area but the ball is thrown to the first base before the batter can run and touch any part of first base, or a runner is tagged out while running or off of the base.  Runs scored by the team on offense must be achieved before the team has had 3 outs recorded against it.
 

  The batter executing a "bunt".  The bat is used as a stopper, to cause the ball to drop onto the field near the batter, and roll only a short distance.  The defense team fielders, who normally would be standing in positions far away from the batter, must try to field this bunt ball and try to throw out this batter going to first base or other runners advancing to the next base.
 

The bunt - in this case, the batter will, instead of trying to hit the ball as hard and as far as he can, will use the bat to merely block the ball, and have the ball drop near home plate, and roll only a short distance from home plate.  When this happens, the runner at first base will race quickly to second base and arrive there safely.  The fielders must still field the ball, but since the runner has already had head start to second base, there will be no chance to tag out the runner going to second base, and so the fielder of the ball will instead throw the ball to first base to get an out on the batter running to first base.  Thus, while the batter is out at first base, he has "sacrificed" himself with an out, so that the original runner at first base can advance to second base.  Then the next batter can try to get a hit to drive the runner on second base to home plate for the run and a score.

The hit and run - this is similar to the bunt, except that the batter will try to hit the ball along the ground in the infield, and with this action, the runner on base will try to run to the next base and reach there before the fielder can field the ball and tag the runner out.  Again, since the fielder may have no play on the runner, the fielder will throw the ball to first base before the batter has run and arrived at first base, thereby throwing out the batter.  In this case, the batter has also sacrificed himself with an out, so that the runner can advance to the next base.

The sacrifice fly - If the team at bat has less than two outs, and it has a runner already at third base, the team may decide to sacrifice the batter with an out in order to try and get the runner home for a score.  It could try the bunt or hit and run as described above, but a more certain option is to have the batter hit the ball as hard and as far as he can to the outfield.  If the ball is caught in the air by one of the defense team fielders, the ball will be a long ways from home plate.  In this case, the runner on third base must touch his base once the ball is caught, but then the runner is free to try and run home for the score.  Usually, the runner can run to home plate faster than the ball can be thrown from the outfield to reach home plate in time to tag out the runner coming into home plate.  Thus, the batter is out by virtue of his batted ball being caught by one of the fielders, but the score has been made by the runner running from third base to home plate.