Does a curve ball really curve?

Because a talented person can throw it so that its' spin is effected by the air and changes it direction.

Becouse when people through the balls they might not throw it correctly or the wind might make them curve

The rotation of a thrown baseball, or any other ball, compounded by the stitching on a ball, creates lift/drag as it moves through the air, accomplishing each type of pitch- fastball, curve ball,...

http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/jon_drobnis/Curveball.html check out this web site Unequal pressure is applied to the seams. The wrist snap creates the rotation. The air presses on...

u put ur middle finger on the seam and the thumb on the other one