Voltage Drop (Vf) is a synonym of the potential difference.
More specifically if a resistor of resistance R is inserted between two points A and of an electrical circuit and traversed by a current of intensity I, Ohm’s law study that the electric potential at A is greater than B in a quantity equal to R-i. In other words, between A and B there is a potential difference, or voltage drop equal to ΔV = R.I.