What does “Balk” mean?

A balk in baseball is an illegal motion by the pitcher, usually meant to deceive a base runner, that results in all runners being awarded one base. Common balks include starting a pitching motion without finishing, failing to come to a complete stop in the set position, making a pickoff throw without stepping toward the base, or faking a throw to first base while on the rubber. The rule exists to keep pitchers from unfairly tricking runners, and while it can be confusing, the penalty is always the same: runners advance one base, and the pitch (if delivered) does not count.