When Beam of light is reflected by smooth surface → reflected rays remain parallel to each other + maintain their spacing. → thus reflection is described as regular (orderly) reflection
In contrast → Rough surface gives rise to irregular (disorderly) reflection → irregular reflection is known as diffuse reflection → because after reflection, rays spread out in different directions.
In Both regular and diffuse reflection → laws of reflection apply for each individual ray. → in case of regular reflection → parallel incident rays → reflected in same direction because surface is smooth. → all rays have same angle of incidence and reflection.
In case of diffuse reflection → parallel incident rays are reflected in different directions → because surface is uneven or rough. → normals at different points on surface are not parallel to one another. → thus angles of incidence and reflection of one ray are different from that of other rays.