A googly is a cricketing term for a bowling delivery that is a variation of a usual leg-spinner delivery. The difference is that instead of the ball bouncing away from the batsman as in a normal leg-spinner, the ball instead heads towards the batsman.
It takes plenty of practice to master the googly technique. First, hold the ball between your bent ring finger and thumb, with your index finger and thumb on the seam. Bowl the ball, with your palm facing upwards and your wrist level with the ground. Using your ring finger to spin the ball anti-clockwise on release, keep the seam of the ball pointing towards the fine leg.
Also known as a "wrong'un" in Australia or a "Bosie" after Bernard Bosanquet, its inventor, the googly is a surprise technique within a leg spin bowler's arsenal. Usually kept in reserve to be used as a shock wicket-taking tactic, it can take a batsman who has lost his focus unawares. If used correctly, the ball can strike the batsman's shin pads for an LBW appeal or else take the wickets outright.
The mechanics of a googly when used against a left-handed batsman obviously change to turn away from the bat, like a leg-spinner delivery would do to a right-handed batsman.