What does sph, cyl, axis on eye exam mean?

Eye glass measures: The sph is the sphere. This is the amount of nearsightedness or farsightedness, measured in units called diopter. Cyl is cylinder. This is the amount of astigmatism. Astigmatism is created when the cornea is not shaped evenly...Egg instead of a ping pong ball. There are other causes of astigmatism. The axis is an angle that indicates where the astigmatism is located.