I have just been reading about John Wallis ( 17th Century English Mathematician) on wikipedia.

https://en.wikipedia.org/wiki/John_Wallis

Can anyone help with this:

the area enclosed between the curvey =x^{m}, the axis ofx, and any ordinatex =h, and he proved that the ratio of this area to that of the parallelogram on the same base and of the same height is 1/(m + 1),

Which parallelogram are we talking about here?