What is the difference between electromotive force and potential difference?

The electromotive force and the potential difference in a circuit are very similar concepts as they are both names for energy per unit charge within a circuit and they both use the same unit, Volts. The difference between the two is that the electromotive force is the voltage, the energy per unit charge, provided by an electrical source, while the potential difference is simply the difference in voltage between two points within the circuit.