What is catcher interferance?

Catcher's Interference is an Umpire's call due to the Catcher making some type of contact with either the batter or his bat during a pitch or does other actions to interfere with a batter's ability to hit the oncoming pitched ball however an Umpire can only call Catcher's Interference as long as the batter is in a legal position while in the batter's box and in the event of Catcher's Interference being called the batter is awarded first base automatically and the runners advanced only if forced to.