A change-up pitch is thrown like a fastball but with slower velocity. Throw an effective change-up with tips from a professional baseball instructor in this free video on baseball.
The change up is a pitch that is named change up because it basically changes speeds. There is some movement involved but basically the change up is a slower pitch than what is traditionally thrown in the fastball mode or what the pitcher might throw as a fastball. The situation is any time that the batter would be expecting a fastball is an appropriate time to throw a change up especially when you're behind in the count like a 2 and 1 count or a 3 and 1 count because generally they are looking for a fastball at that time. There are various various ways of throwing or gripping the change up. The most traditional change up grip is the circle change. Basically you place your largest finger on the seam into the horseshoe, the first finger goes outside the ball in this position, the second finger goes outside the ball in this position and you make a small circle with your thumb and your first finger and that is the basic grip for a circle change. A box change is much similar to the circle change other than you don't make the circle, you simply box the ball with your fingers surrounding the ball. The falcon change is where both fingers are split severely, the middle fingers and first and last fingers are severely outside the ball and that is traditionally known as the falcon change and then there is the choke change which is a little bit like the box change but held way back down in the hand and choked down almost like a palm ball.