A parametric surface is represented by a function from a region of the plane into three-dimensional space. That is, it is given by a triple of functions (x(u,v),y(u,v),z(u,v)), for (u,v) lying in some region of the plane. For parametric surfaces in 3D-XplorMath-J, the planar region is always a rectangle whose edges are specified by giving minimum and maximum values for u and for v.
The Parametric Surfaces gallery is one of several sub-galleries of the Surfaces Gallery. For more information on parametric surfaces, you should see the documentation for the Surfaces Gallery. Note that several other sub-galleries of the Surfaces Gallery also contain parametric surfaces; the Parametric Surfaces gallery contains a miscellaneous collection of parametric surfaces that don't belong in the other sub-galleries.