Light

There are:

Bright Light: sunnd day, well lit room, ...
Dim Light: dawn, night witha full moon, a room with just one torch, ...
Darkness night in a dense forest or coudcover/newmoon, room with closed curtains, ...
Total Darkness: deep underground, room where every window is completly blocked, ... (if theres even a tiniest bit of light its just Darkness)

Darkvision:

Darkvison, even when recived through a spell or magic item, does not work in Total Darkness. Exeptions are Spells of 5th level or higher (ie.casting Darkvision at this level), as well as Items which specifically state to work in Total Darkness. Otherwise, Total Darkness works the same as Darkness, i.e. PCs suffer from the blinded condition, etc.