What does a catcher do?

"Catchers have a very special job on a baseball diamond. They work directly with pitchers to make sure they throw the right pitches, and play a huge role in a teams defense. Readers will go behind the catchers mask to learn just what catchers do and how they impact a teams play on the field. From calling pitches to trying to catch runners stealing, readers will learn all about the important job catchers do on the diamond"--Amazon.com.