What is the difference between the volume of a cone and the volume of the cylinder

The volume of a cone is always 3 times smaller than that of its corresponding cylinder (that is, a cylinder with the same height and base radius).

As in:

Volume of a cylinder = πr²h

and Volume of a cone=⅓πr²h

But just in case you were referring to an actual difference, then that would be ⅔πr²h, since 1-⅓ = ⅔.