Balk

A balk is something that a pitcher does in baseball that is not allowed, or illegal. If a balk happens the umpire will point to the pitcher and yell "balk", and the runners on base get to move up one base. If there are no runners on base, a ball is issued to the batter.
Some ways a balk can happen include;
There are other ways it can happen, but these are the main ones.