We see an object because it emits light (for example, the sun, fire, a light bulb), or we see objects that reflect light.
Diffused light is a soft light with neither the intensity nor the glare of direct light. It is scattered and comes from all directions. Thus, it seems to wrap around objects. It is softer and does not cast harsh shadows.
When a light beam strikes a smooth surface, most of it reflects back in the same concentration. This is specular reflection, which gives us direct, bright light. A mirror is a common example of a smooth surface that causes specular reflection. What happens on a rough surface? Even microscopic irregularities create roughness. The law of reflection is not broken. Each ray reflects back at the same angle at which it struck the object but in a different direction. So diffuse light is scattered light. This scattering is what causes the diffusion and softness of the light beam.
Photographers use the principle of diffuse light to create pictures with vivid details because there are no sharp shadows to distract attention. On a sunny day, they use light diffusers to create soft shadows. Horticulturists are now discovering that diffused light creates a better growing environment in greenhouses. It allows for a greater horizontal spread of light and exposes the middle leaf layers to light. Drivers find that wet roads have a greater glare than dry roads. That is because the cracks and crevices on the road's surface fill up with water, creating a smooth surface. This results in specular reflection that creates the annoying glare. Fog lamps try to make use of the principle of diffused light to provide a safer beam.
The human eye cannot see all the rays on the light spectrum. Infrared rays, for example, are too long for the human eye to perceive, and ultraviolet rays are too short. So, direct (spectral) light seems stronger than diffuse light. However, the total light transmission is the same. Our perception can play tricks on us.