Vision and Light
The most fundamental tasks of adventuring— noticing danger, finding hidden objects, hitting an enemy in combat, and targeting a spell, to name just a few—rely heavily on a character’s ability to see. Darkness and other effects that obscure vision can prove a significant hindrance.
A given area might be lightly or heavily obscured. In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight.

A heavily obscured area—such as darkness, opaque fog, or dense foliage—blocks vision entirely. A creature effectively suffers from the blinded condition (see appendix PH-­‐‑A) when trying to see something in that area.
The presence or absence of light in an environment creates three categories of illumination: bright light, dim light, and darkness.

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.

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 creates a heavily obscured area. Characters 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.

Blindsight
A creature with blindsight can perceive its surroundings without relying on sight, within a specific radius. Creatures without eyes, such as oozes, and creatures with echolocation or heightened senses, such as bats and true dragons, have this sense.

Darkvision Lowlight Vision ~ considered to be 60′ unless otherwise noted.

Many creatures in fantasy gaming worlds, especially those that dwell underground, have Lowlight Vision. Within a specified range, a creature with Lowlight Vision can see in darkness as if the darkness were dim light, so areas of darkness are only lightly obscured as far as that creature is concerned. However, the creature can’t discern color in darkness, only shades of gray. Also know as Eyeshine or tapetum lucidum is when eyes glow in the dark by reflection of light. This can be a range of colors with natural animas and species listed here.

Alligator – red-orange – Dragonborn
Deer – green – Dwarf / Orc
White – Elf & Half-elf
Cat – gold or green – Kaibyō (working title for Cat-folk) & Tiefling
Barred owl – bright red – Owl & Parrot folk

However, since eyeshine is a type of iridescence, the color varies with the angle at which it is seen and the minerals which make up the reflective tapetum lucidum crystals.

Infravision ~ allows a creature to see in complete darkness, though not in or through darkness that is magical in origin up to a set distance. – Dwarf, Gnome, Halfling, Dragonborn. considered to be 60′ unless otherwise noted.

Truesight ~ Provided by spell, item, or effect allows a wisdom save vs invisibility DC of casting.