Basic equation given by (z=x

^{2}/a

^{2}+y

^{2}/b

^{2}) where a and b are

constants.

Cross-sections of the graph parallel to the xy plane are ellipses and cross-sections parallel to the xz and yz planes are parabolas. It looks sort of like a bowl, only it extends to infinity rather than having a brim. This is a standard shape that people first learn in multivariable calculus and such when they actually care about formulas and equations of figures in more than two dimensions.