In baseball, a breaking ball is a pitch that does not travel straight like a fastball as it approaches the batter. A pitcher who uses primarily breaking ball pitches is often referred to as a junkballer. A breaking ball will have some sideways or downward motion on it. Curveballs and sliders are two types of breaking balls.
A breaking ball is more difficult than a fastball for a catcher to receive as they sometimes hit the ground before making it to the plate (sometimes intentionally, sometimes not). The pitcher must therefore have confidence in the catcher, and the catcher have confidence in himself, to block a ball in the dirt when there are runners on base, since if the ball gets away from the catcher the runners will likely advance. If a breaking ball fails to break, it is called a 'hanging' breaking ball. The "hanger" becomes a high, slow pitch that is very easy to hit, and often results in extra bases or a home run.
Whether a right-handed or a left-handed pitcher is throwing will dictate which direction a catcher will turn his body to adjust for the spin of a breaking ball. Therefore, blocking the breaking ball requires some thought and preparation.