glMap1, glEvalCoord funcrions

Dear friends…

I am trying to draw some splines using OpenGL, but I have some question about that; what are the parameters u1, u1 in the function glMap1, and what is the parameter u in the function glEvalCoord.

I looked in the MSDN, but I could not understand what it means.

Please can anyone give me a simple explanation.

Thanks in advance for your help.