Use these options to set the attributes of the tool created when you select . See also Draw NURBS curves.
The higher the Curve Degree, the smoother the curve. The default setting (3 Cubic) works well for most curves.
The knot spacing specifies how Maya assigns U positioning values to knots. Chord length knot spacing distributes curvature better. If you use the resulting curve to build a surface, the surface might display texture mapping better.
Uniform knot spacing produces curve U positioning values that are easier for you to predict.