A left-arm spin delivery turns from the leg side to the off when bowled at a right-handed batsman.
It's bowled in the same way as a right-arm off spinner would deliver a normal off break.
But because it's bowled with the left hand, the ball is released in the opposite direction, meaning it will turn away from the bat.
Most left-arm spinners bowl around the wicket, aiming to drift the ball towards the bat before turning it away.
The middle joints of the index and middle fingers are well spread across the seam. The ball rests against the third finger but the thumb has little involvement.
Turning the wrist and the index finger generate the spin on the ball, turning the ball in an anti-clockwise direction.