Diffuse reflection
Light scattering evenly off a rough surface, so it looks the same from any angle.
See it in WebGL playground. Raise Roughness under Material and watch the shine spread into a soft glow.
In plain words
Most surfaces are rough when seen up close. Light that hits them bounces off in every direction. So the surface looks equally bright wherever you stand. Paper, chalk and cloth reflect light mostly this way. How bright a spot looks depends on how directly it faces the light.