There are an assortment of pitches that can be thrown from the arm of a pitcher. Some are fast, slow, rise, sink, slide and even knuckle. Each different pitch achieves its distinct movement and velocity from two variations. The grip on the ball, and the movement of the arm. Changing the ways that the ball is held and how hard or loose it is held will make determine what pitch is thrown and what that pitch does. It sounds confusing, but it really is not.
The easiest pitch to learn to throw is the fastball. The fastball comes in two distinct variations. There is the two seam fastball, and the four seam fastball. The two seam fast ball tends to move down and in to a right handed batter. It is held loose in the pitchers hand with the index and middle fingers across the parallel stitches on the baseball. The four seam fastball is straighter and held the same way but with the index and middle fingers covering the parallel stitching of the baseball. Both types of fastballs are thrown like you would play catch, nothing fancy to do with your arm or wrist.
A changeup pitch is a slower version of the fastball. It is thrown the same way as a four seam fastball, the only difference is the grip on the ball. For a changeup to be effective, the pitcher must grip the baseball like he is choking it. This action cuts down on the flexibility of the arm and creates less whip action, slowing down the speed of the ball. The changeup looks just like a fastball out of the pitchers hand, but causes the batter to swing a touch early.
The knuckleball is the hardest pitch to learn to throw and master. An effective knuckleball will have no spin coming out of the pitcher's hand, dance and flutter all over the place, and land somewhere near the catcher. It is an extremely slow speed pitch. The knuckleball is held with fingers curled tight so that the fingertips and thumb tip actually hold the ball. When the pitcher releases the ball, he extends his fingers and "pushes" the ball with his fingertips towards the catcher. If not thrown correctly, a very slow, fat pitch will land somewhere a few hundred feet or more away.
A curveball is a pitch that moves in a sweeping arc from the pitchers mound to the catcher. An effective curveball tells the batter that the pitch is not a strike and does not swing. The curveball moves back cross the plate for a strike. A curveball is held by making a "c" with your index finger, middle finger, and thumb. Other two fingers are curled and used as a resting place. Holding the ball loosely, the fingers are placed on the outside of the parallel seams. When the pitch is thrown a twisting of the wrist is involved to put side spin, or english, on the ball. The pitcher's arm ends across his body, palm facing towards first base. Fingers and thumb extended like a toy gun. If the pitcher is young, and the ball is held too tight, repeated using of the curveball has led to early elbow problems.
These are five examples of pitches, what they do, and how to throw them. For descriptive purposes, a baseball is an egg, loosely held means, do not crush the egg. With repeated practice, these pitches can be learned and sometimes mastered.