Texture
The tactile surface quality of a subject as revealed by light, giving a sense of how something would feel.
In depth
Texture is created entirely by raking light: a surface lit frontally shows colour but almost no texture, while the same surface lit at a grazing angle shows every irregularity as a tiny highlight and shadow. This is why texture work is really a lighting decision, and why low sun transforms landscapes and weathered walls.
Examples in practice
Late afternoon sun raking across a stone wall reveals every chisel mark that midday light had rendered flat.