Go to Environment-Weather-Fog-Volume Light

Density: Controls how dense the fog effect is. The higher the value , the more dense the fog is.

Volume Light: The phenomenon of light being scattered by particles in the air, making pathways of light visible.

Scattering: Controls the distribution of the volume light scattering effect. The default value of 0 makes the fog uniformly bright, and adjusting it to 1 makes the fog from the direction of the light source brighter. The higher the scattering parameter, the more pronounced the effect of Volume Light.