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.