TENS stands for transcutaneous electrical nerve stimulation, and it is a method of pain relief that uses a mild electrical current. A TENS machine is a small device with leads connected to sticky pads (electrodes). These pads are stuck onto your skin to deliver small electrical impulses to the affected area, which can help to reduce pain signals and relax muscles. They may also be able to stimulate the production of endorphins, your body's natural painkillers.