Why Electrons only move through a circuit when there is a difference in electrical potential, and that potential difference is voltage, measured in volts. Voltage is often called electromotive force because it is the "pressure" that pushes charge through a conductor. With no voltage difference between two points, no current flows between them no matter how good the conductor is.
Watch out Ampere-hours measure stored charge capacity, such as how long a battery can supply a given current, not the force that starts the current. Capacitance and inductance describe how components store energy in electric or magnetic fields, and they oppose or shape changes in current rather than cause it.
Voltage is electrical pressure; like water, flow needs a pressure difference.