The volt - symbol: V

The volt (symbol: V) is the derived unit for electric potential and electric potential difference (voltage). It is named after the Italian physicist Alessandro Volta. One volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.

In the water-flow analogy, sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage (difference in electric potential) is likened to difference in water pressure, while current is proportional to the amount of water flowing. A resistor would be a reduced diameter somewhere in the piping or something akin to a radiator offering resistance to flow. Perhaps a capacitor could be likened to a U bend where a higher water level can store energy and build up a head of pressure.