What is the potential difference? And how is it created in a battery or a cell?

The potential difference between two points is the difference in the amount of energy that charge carriers have between two points in a circuit. A potential difference of one volt is equal to one Joule of energy being used by one Coulomb of charge when it flows between two points in a circuit.

A battery or cell is a device for storing electric energy. A battery consists of two electrodes, the anode (negative) and the cathode (positive). Usually, these are two different metals such as copper and zinc. These are immersed in a solution (called electrolyte). A chemical reaction results in a potential difference between the two terminals.

The voltage of a battery is also known as the emf, the electromotive force. This emf can be thought of as the pressure that causes charges to flow through a circuit the battery is part of. This flow of charge is very similar to the flow of other things, such as heat or water.

A flow of charge is known as a current.