please explain in detail.
It's a general question. Please submit a problem of your choice and we'll explain and work it out for you.
Anyway following is the way things fall in place.
It's just the difference in potentials at two different points. Let's say two point A and B in an electric field at the electric potentials are VA and VB. What are electric potentials? They are the electric potential energy divided by unit test charge. And electric potential energy is the work done to bring unit test charge from infinite to the given point in the electric field.