The electric potential at a point is defined as the amount of work done in bringing a unit positive charge from infinity to that point. You may wonder what the hell is infinity. It is not practically possible. The concept of absolute electric potential is only theoretical.
What practically exists is the potential difference between the two points. It is defined as the work done in moving a unit charge from one point to another.
In the theory, the term infinity arises because only at infinity we can consider that the electric potential is absolutely zero.