A leg break is bowled by holding the cricket ball in the palm of the hand with the seam running across under all the fingers. As the ball is released, the wrist is rotated to the left and the ball flicked by the ring finger, giving the ball an anti-clockwise spin as seen from behind. When the ball bounces on the pitch, the spin causes it to deviate towards the left from the bowler's perspective; this is to the right from the batsman's point of view, or towards the off side of a right-handed batsman. The ball spins away from the leg side, and this is where it gets the name leg break, meaning it breaks away from the leg. The turn is mostly when the ball pitches.
A leg spin bowler will bowl mostly leg breaks, varying them by adjusting the line and length, and amount of side spin versus topspin of the deliveries.
Leg breaks are considered to be one of the more difficult spin deliveries for a right-handed batsman to play because the ball moves away from their body. This means that any miscalculation can result in an outside edge off the bat and a catch going to the wicket-keeper or slip fielders.
Alternatively, for a ball aimed outside the leg stump, the breaking may be so sharp that the ball goes behind a right-handed batsman and hits the stumps – the batsman is then said (informally) to be "bowled around his legs". The animation on this page illustrates such a delivery.
A left-handed batsman has less difficulty facing leg spin bowling, because the ball moves in towards the batsman's body, meaning the batsman's legs are usually in the path of the ball if it misses the bat or takes an edge. This makes it difficult for the bowler to get the batsman out bowled or caught from a leg break.
A ball bowled by a left-arm unorthodox spin bowler with a leg break action spins in the opposite direction, i.e. from left to right as the bowler sees it. Such a ball is not normally called a leg break but a left-arm unorthodox spinner or "Chinaman".