It is simply the use of a small electrical signal applied to the skin in certain specific ways that appears, at least in some cases to destroy cancer cells as well as possibly some microbes and other organisms. From all evidence so far presented, there is very little risk if instructions are followed and you can even make your own zapper with a little effort. A home made unit, while not as good as commercial units, can have noticeable effects. As a matter of point, even tapping your fingers on the terminals of a 9 voly battery can have some positive benefits.