Hello,
I would like to ask you, why surfaces are just 2d. I know there is Blender manual, but i still can’t get it. You can move vertices to all three sides, so why they are 2d ?. (Sorry for English).
Thanks for any answers.
By “surfaces” you mean polygons? So you’re asking why are polygons 2D? Well with many polygons joined together you can create a 3D shape. But the “walls” are still 2D.
I hope that answers your question.
Oh and by the way, welcome to BlenderArtists! 
Sorry, I mean surface objects (those, which you can add by Add > Surface). Anyway, thanks for answer.
Why do you say they are 2d?=P
I found it in book, and it’s written in this link too http://wiki.blender.org/index.php/Doc:Manual/Modelling/Surfaces. So I think they are 2d, aren’t they ?
He means the faces themselves are 2D.
A cube, is made up of 6, 2D squares.
Well I guess technically a NURBS surface is a 2D face with it’s edges oriented not only on the 2D axis (x + y) but also on the Z axis. It’s really an abstract concept. A 2D polygon (if I may use the word) with it’s vertices (or edges) moved into a third dimension.
if you add nurbs surface, it is not 2d. maybe you need to change your viewpoint in 3d view?
Alright, now I think I finally got it. I asked my math profesor today, and she told me basically the same thing as Robo3DGuy: Surfaces are just 2d, but they have polygons moved to third dimension. We should ignore enviroment and look on them only. Sorry for bad English. Thanks a lot to your answers.