There are different potentials related to different fields of force. Electric potential , magnetic potential and gravitational potential. Perhaps there are more such quantities.
1. Electric potential at any point
It is the energy (or work done) per unit test charge required for it to be brought from
infinity to that location. Electric potential difference is the difference in voltage or potentials between two points in space or in a dielectric medium or in a conductor (or resistor). It is a scalar quantity.
Its units are Volts or Joules/ Coulomb or Watts/Ampere, or Newtons-meter/Coulomb.
If the electric potential is same at two points
in a circuit or in space, then there is no current flowing between them. Current
flows from higher potential towards lower potential in a circuit. The
electric potential difference between the two terminals of a cell or battery is called EMF
or electromotive force.
Potential difference is also the product of electric field and distance between points. Potential difference is also equal to the charge passing between the two points per second, when a 1 ohm resistor is connected between them.
V = E * d = F * d / q = P / Ampere = I * R = q * R / t = U / q
2. Gravitational potential difference
It is the energy required to bring a unit mass from infinite distance to its point in a gravitational field of other masses. Potential difference is the difference between potentials at two points in space or in masses. It is a scalar quantity.
Units are Joules/kg. potential difference due to a mass M between two points at distance of d1 and d2 from M is - GM [ 1/d1 - 1/d2 ]
3. Magnetic potential difference
It is defined as Curl of magnetic field. It is more complicated than the above.