Explain acceleration as it relates to a baseball being thrown through the air.

Acceleration of the baseball as it is being thrown is the rate at which the velocity of the ball is changing

Assuming there is no air resistance.

After the ball leaves the hand, the acceleration remains constant. i.e. it is 9.8 m/sec^2 directed vertically downwards, and stays at this value until the ball is caught.

This is rather different to what happens to the velocity and displacement during this journey