EvilEye:
Thanks for the clarification; my puny brain just can't fully grok it. And maybe I never will--I'll just have to accept it.

I can kind of "get" the idea of a surface of paper made 3D, just as I can get the dimple mass makes in the trampoline made 3D. But, I don't "get" the idea of a CURVED surface (e.g.: sphere, torus, saddle, etc) made 3D.

I wish there were some example or analogy that could help...beyond what's already out there (like linked to the Astronomycast site) where all they show you is a sphere with a triangle on it. That just reinforces my inability to comprehend that surface, and not the solid content below the surface, as being 3D. *shrug*

Oh well.