Electric current is a flow of electricity through a medium and its SI unit is the ampere, with the symbol A. The flow is typically through a wire and composed of electrons, the tiny particles that make up electricity.
The ampere is that current which, if maintained in each of two infinitely long parallel wires separated by one meter in free space, would produce a force between the two wires (due to their magnetic fields) of 2 x 10-7 newtons for each meter of length.
The SI unit of electric potential difference is the volt (V) 1 V = 1 W/A
The SI unit of electric resistance is the ohm (Ω). 1 Ω = 1 V/A.
The SI unit of charge, the coulomb, "is the quantity of electricity carried in 1 second by a current of 1 ampere". Conversely, a current of one ampere is one coulomb of charge going past a given point per second.