Lets you draw a NURBS curve by placing CVs.
The higher the Curve Degree, the smoother the curve. The default setting (3 Cubic) works well for most curves. You must create at least one more CV than the Curve Degree number. For example, you need at least six CVs to complete a degree 5 curve:
See Degree for more details.
The type of knot spacing sets how Maya assigns U position values to edit point (knots). Chord length knot spacing distributes curvature better. If you use the curve to build a surface, the surface might display textures better.
Uniform knot spacing creates curve U position values that are easier for you to predict. See Parameterization of NURBS curves and surfaces for details.
If you create a pair of curves with Multiple End Knots off, you can use Snap to Points to align the second CVs (next to the end CVs) of each curve to create tangent continuity between the two curves.