I see a lot of teams that have there shortstop and 2nd baseman gives signs to the outfield to know what the pitcher is throwing. Why do they give signs to the outfield?
So the outfield is aware of where the batter may hit the ball and adjust where they play accordingly. For example, an outside pitch against a right-handed hitter is likely to be hit to right field.
easiest way for outfielder to understand is, IF Pitch is to the side of the plate they are playing on the field, there is a better chance the ball can be hit hard to their side of the field (Extension of the arms), if the pitch is to be AWAY from their side of the plate, good chance for a softer hit ball (RH Trying to pull an outside pitch, or inside pitch off hands is weak to the right side) and the fielders away from the pitch should anticipate a blooper or slow roller.
yup - the changeup! Especially for the corners! I tell my 3B if she gets a change up called inside to a RH - be READY as batters today are learning to handle changeups!