IT IS THE SI UNIT OF ELECTROMOTIVE FORCE.
Let q = electric charge..
Let V = voltage which is also known as the potential difference or just potential.
The work done when a voltage V pushes or pulls a charge across the potential is WE = qV.
here's the reason.
F = qE + q(V X B) IS THE TOTAL FORCE ON q in an electric field E and a magnetic field B. if B = 0 , then there is no magnetic field. we have F = qE AND
E =V/h between two parallel plates h distance apart. Thus
F = qE = qV/h and Fh =qV which shows a force F acting over a distance h and that is work. QED
AS WE = qV is work and work is expended energy, we often see electrical energy written in electron-volt units.