A volt is the measure of voltage or pressure pushing electrons. Compare it to a water faucet. When the faucet is off there is still potential to flow, but the valve holds back the pressure. Voltage is the electrical pressure that causes current to flow. In technical terms, one volt is the amount of pressure required to move one ampere of current through a resistance of one ohm. Most vehicles have 12-volt systems, while most homes have 120-volt systems. Another difference in most home and vehicle electrical systems is the current. Automotive batteries provide Direct Current (DC), while homes use Alternating Current (AC).