In baseball, a stolen base occurs when a baserunner successfully advances to the next base while the pitcher is delivering the ball to home plate. In baseball statistics, stolen bases are denoted by SB.
If the defense makes no attempt to put the baserunner out (for example, if the catcher doesn't even look his way), the play is scored as defensive indifference (also called fielder's indifference), and no stolen base is credited to the runner. Defensive indifference is generally only scored instead of a stolen base when the game is in a late inning and the team with the stealing baserunner is down by more than one score. MLB Rule 10.07(g) covers defensive indifference.
Successful base-stealing requires not just simple running speed, but also good base-running instincts, quickness, and split-second timing. The scoring and criteria for awarding a stolen base to a runner are covered by rule 10.07 of the Major League Baseball rule book.