Most hitters have a swing ; the swing goes to the ball or across the ball, the correct swing however (especially for power hitting or hitting the ball hard) must go through the ball . There is a difference between the guys who get paid and everybody else's swing. They have a "trained " swing that goes out through the ball . This is done by using the "knob of the bat "to delay the swing until the bat gets in front of the body then the swing takes place. If the hitter can do this on a regular basis he can name his price come contract time in the free agency market. For kid's just starting out the  they must learn that the  "knob of the bat" is the brain's of the whole operation of a good swing or a Full extension swing ( one that goes through the ball and not across the ball) . The knob must be on the inside of the pitched ball and going out toward the ball on a 30  degree angle FIRST then the barrel of the bat will follow the knob to make solid contact through the ball and you end up with the lead hand of the bat turning over and finishing up high. MIKE