Sorry, I've always called it warping the texture space. I see that there's strong precedent for the term 'domain distortion' in various fields, so perhaps I should have called it that. The addition of the word domain or texture coordinates or something might have helped.
The things that are made up of polygons are called surfaces in TG, to distinguish them from volumetrics/atmospherics. I can't call the actual surface a material because a material is something which is assigned to a surface, not the surface itself. (If we're using other 3D apps as an example.) Actually, underneath the GUI I use the term 'material' to assign whole shader trees to a particular surface, e.g. the planet, or a leaf of a plant, but the whole planet or the whole leaf has the same material (in standard 3D app terminology). You don't ever get to use the term material in the GUI because it's represented by the final shader connection to the planet. A material is built up of shaders, and that's where the real work needs to be done. Maybe Surface Layer could be called Material - is that what you meant? But really it's not - it's a smaller component than that, it's just one shader which builds up a whole material which is implied by the connection to the planet. If there were a separate list in the GUI for object parts and the materials assigned to them, then yes I would call them materials, but right now they're defined by the final shader in the shader tree which makes up their materials.
Matt