White balance is an adjustment to correct and neutralise colors captured with different light sources. The color of light can vary considerably depending on the time of day and whether you’re shooting in natural light or under artificial light.
Auto white balance
Auto white balance is the default setting for most photographers. The camera will attempt to determine the color of the ambient lighting and adjust the camera's processing to produce natural and neutral-looking colors. It generally works well, but can often fail to correct fully for very yellow-orange artificial lighting, and can overcorrect the natural color in landscapes at the start and end of the day.
Some photographers use white balance presets to fix the camera's rendition at specific settings, others shoot RAW files and choose the white balance setting during RAW processing later.