A curve in Rhino uses NURBS equations to represent a curve in 3D space. Control points are the coefficients used in the NURBS equations. A curve is either open with two ends, or closed.

A polycurve in Rhino is two or more curves joined together. Each pair of curves coincide at one end of each curve. Only two curves can coincide at a point. For many but not all operations a polycurve is treated as a single object. A polycurve is either open with two ends, or closed.

A surface in Rhino uses NURBS equations to represent a surface in 3D space. Control points are the coefficients used in the NURBS equations.

A polysurface in Rhino is two or more surfaces joined together. Each pair of surfaces coincide along an edge of each surface. Only two surfaces may coincide along an edge, but more than two surfaces may coincide at the corners of the surface. For many but not all operations a polycurve is treated as a single object.

A solid in Rhino is a surface or a polysurface which is which is closed. Closed means that there are no edges which do not coincide with another edge. The surface of the solid is represented by the surface or polysurface.

Control points are available for curves, polycurves and surfaces. Control points are not available for polysurfaces.