Hi Mike, Control points and knots are different things, both of them are things that go into the definition of the curve or surface though.

Knots set up what are called "basis functions" which is one thing that controls how much a particular control point affects the curve like if it pulls the curve more strongly towards the point or not. Then just to be even more confusing there is also another thing called "weights" that go on control points that also has a kind of similar "strength of pull" effect as well with the main difference being that the weights can pull in just the exact way to make conic section shapes like a circle or ellipse.

But the main type of thing that is usually removed for a NURBS surface is a knot, which then has a side effect of also removing a row of control points as well.

- Michael