Electric potential difference, often referred to as voltage, is a measure of the change in electric potential energy per unit charge between two points in an electric field. It represents the work done in moving a unit positive charge from one point to another, against the electric field. Voltage is a scalar quantity measured in volts (V). When a positive charge moves in the direction of increasing potential (higher voltage), work is done on the charge by an external force. Conversely, if it moves towards lower potential (lower voltage), it releases energy. Electric potential difference is fundamental in understanding and analyzing electrical circuits, providing the driving force for the flow of electric charge, and facilitating the transfer of energy in electrical systems.