Question

what is potential difference?​

Answer 1

Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points. The difference in electric potential between two points in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points. 

Answer 2

Potential difference (V) -- is measured in volts (V). Potential difference is the work done per unit charge. A potential difference of 1 V means that 1 joule of work is done per coulomb of charge.