Electric Potential: Scalar quantity, like height. Electric Field: Vector quantity, like the slope of that height.

Electric Potential: Scalar, like height. | Electric Field: Vector, like the slope of that height.

Use scalar superposition: sum the individual potentials from each charge: $$V=\frac{1}{4 \pi \varepsilon_{0}} \sum_{i} \frac{q_{i}}{r_{i}}$$.

Chemical processes in batteries create charge separation, resulting in electric potential differences.

Electrons move until they reach the same electric potential.