What "balk" means in baseball

In baseball, balk refers to a forbidden act by a pitcher to deceive a runner or a batter. It is basically a fake pitch or an illegal motion that can allow the runner to advance to the next base. If a balk is called by the umpire, it will result in all the runners getting to advance one base without the possibility of an out being made on that play. Pitchers tend to be very careful about following the balk rules, as it can give their opponents an advantage.