The white balance control is to make the white objects in the actual environment appear "true" white in the picture you shoot. Light sources of different natures will produce different color trends in the picture. For example, the light from candles will make the picture more orange, while the light after dusk will put a blue cold tone on the scene. 

And our visual system will automatically compensate for different light, so no matter in the warm or cold light environment, we look at a piece of white paper is always white. But the camera is not the case, it will only directly record the colors presented in front of it, which will cause the picture to be warmer or colder.

Type of light source color temperature value
Electronic flash light                5300-6000               1000-5000 WHalogen lamp             5000-6000
High color temperature carbon arc lamp                5500                       White carbon arc lamp                         5000
500W High color temperature photography light        3200                        500W Photography floodlight                3400
Photography halogen light                 3000-4000               1300W News iodine tungsten lamp              3200
200W Ordinary bulb              2980                        100W Ordinary bulb                    2900
75W Ordinary bulb                 2800                        40W Ordinary bulb               2650
Candle light                           1850 

Used for color cameras to ensure correct color representation under different color temperature environments

There are two types of white balance functions of the camera: automatic white balance and manual white balance. Automatic white balance is that the camera can automatically perform white balance correction within a certain color temperature range according to the shooting light conditions without intervention. The color temperature range that can be automatically corrected is approximately between 2500°K-7000°K, and beyond this range, The camera will not be able to perform automatic correction and cause the color of the shooting picture to be distorted. In this case, the manual white balance function should be used to correct the white balance.