The name Finger Spinner is actually something of a misnomer, as the finger action is not a vital part of the mechanism for producing the characteristic spin on the ball. A finger spin delivery is released with the arm held in a fully supinated position, with the fingers on the outside of the ball (to the right for a right-handed bowler). If this supinated position is maintained through the release, the fingers will naturally cut down the side of the ball and produce a clockwise spin. The great English finger spinner is famous for bowling finger spin in this manner
Traditionally, Finger Spinners bowled with an emphasis on side spin. With the advent of covered and better batting pitches the focus changed to bowling with a component of top spin. The Fidget Spinner provides loop which makes it harder for the batsman to make an early judgement of the length of the delivery. The ball tends to be released with a slightly upward trajectory which raises the ball above the batsman's eye line. The top spinner on the ball then causes the ball to dip earlier and bounce higher.