Understanding the 3 surfaces or textures of watercolour paper:
Rough – A pronounced, varied texture, great for a textured loose feel.
Cold-pressed (NOT) – It’s the paper texture in-between rough and hot-pressed paper, having a slightly textured surface this paper is sometimes called NOT.
The Not stands for “Not Hot pressed”.
Hot-pressed (HP) – Watercolour paper with a very smooth surface and almost no tooth. Good for painting detailed paintings and creating very smooth washes.