A TENS machine is small -- about the size of an iPad mini. It’s connected to a series of electrodes, which are put on your skin to deliver a low-voltage electrical charge. The electrical pulses stimulate nerve fibers in the area where you have pain and reduce the pain signals to your brain. The electrical charge may also cause your body to release natural hormones that decrease your pain levels.
You can get TENS treatments from a machine you use at home or from a device at your doctor's or physical therapist's office.