To understand why you might need to adjust the white balance in your camera, you first need to understand color temperature.
Adjusting the white balance basically means making sure that a part of the picture that is supposed to be a neutral color does actually contain equal amounts of red, green and blue. We call it white balance but it works equally well with light gray parts of the scene, however generally speaking the lighter the better. If the gray parts of the picture are indeed rendered gray then it follows that all the other colors in the scene will be rendered in a natural looking way.

On most modern cameras we have an AWB (automatic white balance) setting, various fixed color temperature settings such as 'daylight', 'tungsten' and 'flash' and, on the better cameras, a custom setting.
Most of the time we can set the white balance to automatic and forget all about it. Generally don't loose too much sleep over the white balance setting of your camera as, provided it is not too far out, the color balance can be changed in the computer. The auto setting gives a reasonably accurate rendition in daylight or with flash and the odd tweak in the computer is no great hardship.
If we were going to shoot pictures indoors without a flash then we would definitely set the WB to the 'indoor' setting, as the difference in color would be too great to ensure good color in the editing. However, 99% of the time, like most people, we either shoot in daylight or use flash.
There is though, no substitute for getting it right in the camera and it can sometimes save you a lot of work later on.
Below is a chart showing the different white balance settings on a typical DSLR camera. Your camera may have more settings than this or less or even slightly different ones.

AWB (automatic white balance) is the default setting and the one you should use most of the time. Daylight, shade, cloud, flash and tungsten are all fixed settings that you can use under the appropriate lighting conditions. Have a look at the color temperature chart to understand what they do. Basically they are like the old filters that users of film would screw onto the front of their lenses to compensate for different color temperatures. The advantage of using these fixed settings as opposed to the AWB is that a predominance of one color in your scene will not cause the camera to give a false reading. Click 'NEXT' and proceed to the next module.