There is no precise number of dimples on a regulation golf ball, but most manufacturers design golf balls that have between 300 and 500 dimples. The more dimples a golf ball has, the higher the ball will fly.
If a ball has too many dimples on it, it will fly very high but not very far. Golf balls were originally smooth, but golfers realized that as the golf ball gained dents and nicks it flew further. The dimples on the golf ball help to create the spin on the ball into lift, making the ball fly higher and further. The dimples on a golf ball are complexly arranged to control the spin and further improve the distance.