Direct light—Direct light is light that shines directly from your source (such as the sun) into your eyes. Excessive direct light can obscure the details of the surrounding environment and make it difficult to focus on the line of sight.
Reflected light - reflected light is often in the form of glare. Reflected light is light that is reflected back to the eye from a reflective object. Like direct light, intense reflected light makes it difficult to perceive details or look directly at an object. Snow, water, glass and white sand are good reflective surfaces.
Diffuse light—Diffuse light is light that bounces and disperses in many directions, so it seems that this light does not have a specific light source. A typical example of diffused light is the glow over a large city. It is difficult for us to determine a single source for it. When there is no direct light source, we can still see things, which is the credit of diffuse light.
High-quality sunglasses eliminate UV rays in the spectrum, reduce direct light, make people feel comfortable, and eliminate or reduce reflected light (depending on the reflective surface).
An interesting feature of light is polarization. When reflected from certain surfaces, such as the water surface, the light is polarized. Polarized sunglasses eliminate light reflected from water or similar reflective surfaces due to the polarized nature of the reflected light.