White balance is all about getting accurate color in our images; images with no unwanted color casts.
Did you know that light comes in different colors - well different color temperatures to be more accurate? Sunlight, a lightbulb and the light on a cloudy day all have different colors that are detectable by our cameras even when we don't perceive them with our naked eye (because our brain corrects things for us). We've all returned from a shoot and found our images all had a yellow, green or blue tinge to them. In order for us to get the colors in our photographs as accurate as possible, we have to adjust the white balance in our cameras for the kind of light that's around when we're shooting.
There are several ways you can avoid problems in the white balance arena:
First, you could shoot on Auto White Balance which will mean the camera will do its best to read the lighting situation it finds itself in and make appropriate adjustments. This really does work fairly well, especially outdoors.
Or, you could select the Preset White Balance Setting on your camera that best matches your surrounding light, like: Incandescent (indoor light bulb light), Fluorescent, Direct Sunlight, Flash, Cloudy, or Shade.
You could also create a custom white balance, which may sound complicated but it really isn't, you simply make your camera read the lighting where you are by reading the light off of a grey or white card and creating your own "preset". Trust me it's easy, I've been doing it all morning with great results, after reading the salient three paragraphs in my manual.
Lastly, you could simply shoot in RAW rather than JPEG. This doesn't avoid white balance issues but it does allow you to select the correct white balance in post-processing in software like Lightroom. Having said that, remember what the pros do ... they do their very best to get it right in the camera, up front. It certainly saves lots of processing time later - time that could be better spent shooting.