Rhino can work with many different classes of objects, including:
CURVES In Rhino, “curves” may be closed or open; they include actual curves as well as straight lines; they may be restricted to 2D or may occupy 3D space. This class includes lines.
SURFACES are infinitesimally thin, arbitrarily flexible “sheets.” Represented by outline curves and “isocurves” interior to the surface. In Rhino, surfaces are represented and constructed using the NURBS mechanism.
POLYSURFACES are objects consisting of two or more surfaces joined together.
SOLIDS are equivalent to completely closed surfaces and polysurfaces (e. g., spheres, boxes). However, note that Rhino solids are always hollow, like SketchUp solids but unlike AutoCAD solids.