The dimples on a golf ball make it fly farther and faster than it would have without them. This is due to the fact that dimples increase turbulence and decrease drag on the ball. They do this by making the air stick to the ball a little longer than it would have otherwise and reducing the turbulent wake that is behind the ball as it is flying. This reduces the area of negative pressure behind a flying ball and makes it fly faster and farther.
More about dimples on a golf ball:
Dimples were not intentionally added to the golf ball until 1905, although the game of golf has been played since the 1400s.
Players first got the idea to add dimples by noticing that scuffed up and scratched balls flew farther than smooth ones.
The number of dimples on a golf ball can range from 400 to 1,000.