TENS is an acronym for Transcutaneous Electrical Nerve Stimulation.
A TENS unit is a device that transmits small square electrical pulses to the electrodes, which transmit this electrical pulse to the underlying nerve. Pads are placed on or near the area of pain. Soothing pulses are sent to the pads, through the skin and along the nerve fibres. The pulses (controlled by the user at all times) suppress pain signals to the brain is a highly effective treatment for pain.
TENS are used worldwide and recommended by sports coaches, physiotherapy departments, pain clinics, doctors and other medical practitioners.