Question

What's difference in [electric potential energy, electric potential difference, Electric potential due to point charge] with definition???

Answer 1

" A potential difference of one volt exists between two points when one Joule of work is required to move one Coulomb of charge from one point to the other" 

Between two points A and B we may write
WAB  =  -VAB q

where VAB = VB - VA  is the potential difference between A and B.