It's like walking barefoot. It connects you to the earth.
The research done so far shows it helps reduce inflammation.
You can use conductive sheets when you sleep or pads for feet indoors so you can be earthed or grounded as much as possible. It's one of the most promising things for inflammatory problems I've heard of. You can make them yourself if you know how and can get the materials, it's like just conductive materials and wires to connect them to an earth rod.