White Balance is when you adjust the colours on your camera to help make an image look more natural. You can change the white balance to make the camera take warmer or cooler images. The impact of this is the image looking more like how our eyes perceive colours and light.

As you can see, first set of images (inside using mostly artificial light) have much more of a distinction between each picture, where as the second set of pictures (using mostly natural light) are much more similar to one another.