Light reaches areas that are not in direct light by means of

Light reaches areas that are not in direct light by means of scattering.

The scattering is a phenomenon taking place with light, when the particles absorb light and emit it in different direction with intensity less than the original intensity is called scattering.

For example: There is a small room with a single window. The space within the room has no direct light resource but the light passes window and lightens the whole room. Even though the size of the window is smaller than the size of the room, it can light the whole room because of the process called scattering.