A TENS unit, or Transcutaneous Electrical Nerve Stimulation unit, is a device used to relieve pain. It works by sending low-voltage electrical currents through the skin to stimulate the nerves. This stimulation can help reduce the perception of pain and promote the release of endorphins, which are natural painkillers produced by the body. TENS units are often used for various conditions, including chronic pain, arthritis, and muscle injuries. They are typically portable and can be used at home or in clinical settings. Users place adhesive pads on the skin near the area of pain, and the device is adjusted to deliver the desired level of stimulation.