Ambient light is the existing available light present in any environment. Ambient light can be subdivided into four major categories:
Daylight - A mixture of sunlight and skylight. Sunlight is the dominant or main light. It is warm in color and creates highlights and shadows. Skylight is the secondary light. It is cool in color and fills the entire scene with soft diffused light. Without the action of skylight, shadows would be black and detail would not be visible.
Tungsten - A common type of electric light such as household bulbs/globes and photographic lamps. A tungsten element heats up and emits light. Tungsten light produces very warm tones when the white balance is set to daylight. Make sure you adjust the white balance to the dominant light source or capture in the RAW format and set the white balance in post production.
Fluorescent - Fluorescent light produces a strong green cast (not apparent to the human vision) if captured using a daylight white balance. If used as a primary light source the results are often unacceptable due to the broad flat light from above. Underexposure is again experienced when using this light source and the cast can be difficult to correct. Fluorescent light flickers and causes uneven exposure with focal plane shutters. To avoid this shutter speeds slower than 1/30 second should be considered.
Firelight - Light from naked flames can be very low in intensity. With very long exposures it can be used to create atmosphere and mood with its rich red tones.