As I understand it, our bodies are at a positive potential in relation to the earth. In our natural state, barefoot, we were in electrical contact with the earth, at the same potential as the earth.
In order to not take up unnecessary space in the forum I wrote an in-depth review about my experience
here. Feel free to take a look if you're interested.
The benefits (as reported in the book Earthing) range from relief from arthritic pain, to better sleep, to more energy, and so on. I've been using an earthing pad for about 10 days now and I
do feel very energetic with few aches or pains.