Question

what is difference between potential, potential difference, voltage, emf

Answer 1

Potential is the energy stored because of position. In electrical terms, In order to move an electron in a unit positive charge electric field (moving away from charge) to a particular point, you need to do some work.This work is called emf. This work is saved as energy at that point. This energy is called potential. This amount of work will be varied from point to point.
Suppose you have 2points in the above electric field the energy difference between of those points is potential difference between those points i.e. you need to do that much work if you want to move electron from the first point to second point.
Voltage and potential difference are similar.

Answer 2

Potential, Potential difference, Voltage, and EMF all refer to the same physical concept, they're just different names for the same thing. However, you should refrain from using emf if you can, because it implies that the electric potential is a force.