A TENS unit is one of several kinds of electrotherapy devices that use very small doses of electric current to promote natural pain relief. The word TENS, sometimes abbreviated as T.E.N.S., stands for Transcutaneous Electrical Nerve Stimulator. The TENS machine itself is a small electronic device that delivers current through electrodes placed on the skin. Unlike systemic drugs, which affect the entire body, electrotherapy targets pain exactly where it occurs. A modern TENS unit is easy to use and compact enough to provide quick and dependable pain relief at work, home or play.