Ambient lighting is any light that a photographer does not add into their composition intentionally. Ambient lighting comes in many forms. Ambient light is the light already in the studio or shooting location without the photographer doing anything else.
Ambient lighting can be helpful or frustrating depending on the intended style and end product you are trying to achieve as a photographer or videographer.
You might have to decide to add light to the scene or get creative about blocking or modifying the ambient light.
Types of ambient light
Since ambient light is any source of light already available, it could be natural or artificial light. "Natural ambient light" is a term generally only used to describe sunlight or moonlight.
Once you modify the ambient light available, you might call it "modified ambient light" or describe more thoroughly what kind of lighting was used. Calling modified ambient light "ambient light" can be controversial to some professionals in the industry.
For example, ambient light could come from any of the following artificial light sources:
Streetlights
Car headlights
Lanterns
Lamps
Light-up signs
Ambient light could also come from any of the following natural light sources:
Sun
Moon
Bioluminescence
Fire
A photographer might be able to depend on a fixed light source, such as a streetlight, but not be certain about the consistency of bioluminescent light.