Surfaces are attributes, defined at Options > Element Attributes > Surfaces.
Surfaces include a color, cover fill, and optional texture.
Surfaces defined here are assigned to construction elements through Building Materials.
Surfaces are displayed in the 3D Window, Section/Elevation/IE and 3D Documents, and in PhotoRenderings. You can also use their color and texture in 2D Fills.
You can override the Surface at the element level: use either Surface Painter, or element settings.