The presence or absence of light in an environment creates three levels of illumination: bright light, dim light, and darkness.

BRIGHT LIGHT

Bright light lets most creatures see normally. Even gloomy days provide bright light, as do torches, lanterns, fires, and other sources of illumination within a specific radius. A day of bad weather such as raining or snowing halves the distance a creature can see.

DIM LIGHT

Dim light, also called shadows, creates a lightly obscured area. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light.

DARKNESS

Darkness creates a heavily obscured area. Creatures face darkness outdoors at night (even most moonlit nights), within the confines of an unlit dungeon or a subterranean vault, or in an area of magical darkness.