what is applied potential diffrence and why and how do we use it?

let us say there is some charge say +Q in some region. if we want to define a potential at some point in this region, it is defined as follows.

Potential at that point is the amount of work done in bringing a unit positive charge from say infinite location(far location)  to this point.

far location means location where there is no presence of electric field that is generated by +Q charge.

we can potential at different points in this +Q region.

Take any two points , take the diffrence between them that will give the potential difference between those two points.

if there is some finite difference between these two points , then charge will flow across those two points whenever there is some conducting material between them. this is used to generate current