Hard edges and curved surfaces I'm quite new to Blender(and 3D graphics in general) and I can see that there is only 2 kinds of 3d surfaces, meshes and NURBS, meshes only have hard edges, while NURBS have only got curved surfaces, so my question is there any type of surfaces that provides curved surfaces and hard edges?
For visual purposes it is sufficient to approximate the surface with a mesh / wire and use smooth shading afterwards to make the surface appear smooth.

Same mesh using flat shading(top) and smooth shading(below)


To create curved surfaces the common approach in blender is using catmull-clark subdivision.

Catmull-Clark subdivision using crease edges(pink)