Introduction - If you have any usage issues, please Google them yourself
Bezier Curves.
These are two programs that use Bezier curves. Bezier curves are simply lines, with one or more control points that "attract" the line toward it. One is a Bezier curve in 2D, the other is a Bezier surface in 3D. Both allow you to select control points and move them around in the window, which affects the shape of the curve.