A Bézier surface is a special case of a non-uniform B-Spline.
The knot vectors have exactly two knots, normally 0 and 1, which are multiplied
by the surface order in both parameter directions. For example,
the knot vectors of a bi-cubic (order of 4) Bézier surface are
both 
.
A Bézier surface can also be rational. A bi-cubic Bézier surface
together with its control mesh is shown in Figure 1 and a
Bézier surface of 
order in Figure 2.
Figure 1: A 
order Bézier surface together with its control mesh
Figure 2: A 
order Bézier surface together with its control mesh