White Balance :
Because the camera is an electronic piece of equipment, it needs to be told what is white. The temperature of sunlight is 56 Kelvin and tungsten light has a temperature of 32 Kelvin. The camera can not distinguish between the two.

Our eyes automatically adjust to the difference in temperature and so we see white, no matter what white we are looking at. The camera has to compensate for the difference by using filters, one for sunlight and one for tungsten. You choose what filter to shoot through in order for the camera to see the proper white.

Indoors:
Tungsten light is light from an ordinary light bulb. The hot filament glows at a temperature of 32 Kelvin, which is orange.

Florescent light has a wide range of temperatures in the green area. Turn them off if at all possible, because they give a very flat and washed out look.

Outdoors:
The sunlight goes through the atmosphere and the atmosphere is blue. Thus the temperature of sunlight, 56 Kelvin, is blue.

TIP: When the sun is on the horizon either at sunrise or sunset, the temperature changes to 32 Kelvin, which is orange.

Because the temperature is the same at both times of day, you can shoot dusk shots in the morning and morning shots in the evening. They will look the same. This is called the magic time.