The white balance button (also known as the color balance button) adjusts for the color of light.

To understand white balance, you first need to understand the notion that every light source has a different color. The sun, for example, has a bluish tone (which is why the sky looks blue). Fluorescent lights are greenish, and incandescent light bulbs are orangish. Car headlights are beet red. You probably don't realize this because human eyes have a near-magical ability to compensate for these color variations and make everything look normal.

In recent years, cameras have become pretty good at doing what our eyes can do--that is automatically adjusting for the overall color of a scene. Yet, professional cameras retain a "white balance" button to ensure that operators can control the color when they choose.