I don't want to take this thread too off topic, so here's the short answer.

It's a sheet with either copper or silver threads that's connected to a grounding wire that is connected to the earth either directly or through a grounded outlet in your home. The intent is to re-connect you to the earth and its regulating EMF. It can help dissipate unhealthy charges built up in the body.

Very few of us spend anytime directly connected to the earth. Unless you spend time going barefoot outside or hug a tree, we are pretty much disconnected. So you can just go outside and place your feet on the bare ground for about 45 minutes a day. You are also connected when taking a shower as long as your pipes are copper and go into the ground.