The potential difference between two points is said to be volt if work is done in transferring coulomb of charge from one point to another point isJoule.
In other words, Potential difference is the difference in the amount of energy that charge carriers have between two points in a circuit.
Or potential difference is the measure of the stored energy in any form.
The S.I. Unit of potential difference is Volt.
Voltage:
Voltage is the work to be done upon a unit charge to move between two points against a static electric field.
Voltage is also known as electromotive force emf, electric pressure, or electric tension.
A voltage which is a measure of electric potential difference is the cause of electrical current to flow in a closed circuit.
Mathematically, Voltage = Work done (W) / Charge (Q).
Thus the unit of voltage is joule/coulomb.
Hence potential difference and voltage are different.