Whitening your teeth is simply making your teeth a lighter, more attractive shade.
Genetics play the greatest role in the shade of our teeth. The foodstuff that we put in our mouths also plays a role regarding the shade of our teeth. The most obvious staining materials are smoking, tea, red wine and coffee.
There are some over the counter whiteners. Usually these are surface stain removers. To whiten what Mother Nature gave us usually requires a professional strength material to alter your shade.
After whitening, most people will need to do a "boost" treatment about once a year.