Potential difference, also known as voltage, is the difference in electrical potential energy between two points in an electric circuit.
Potential difference is measured using a voltmeter, which is connected in parallel to the circuit and measures the difference in electric potential energy between two points.
A potential difference of 1200 V means that there is a difference of 1200 joules of electric potential energy per coulomb of charge between two points in the circuit.
The potential difference determines the amount of kinetic energy that an electron gains when it moves through an electric field. In this case, a potential difference of 1200 V gives an electron 1200 eV of kinetic energy.
Potential difference is directly related to electric current, as it is the driving force that causes electrons to move through a circuit. A higher potential difference will result in a higher electric current, while a lower potential difference will result in a lower electric current.