Current is the rate of flow of charge. In other words, current is a measure of the net charge that passes by a point in a circuit in a given time interval.

The symbol for current is I. The unit of current is the ampere (A), or amp for short.

I = dQ/dt

ΔQ = ∫ I dt

Although current in most cases consists of flowing electrons, the direction of the current on a circuit diagram is shown as the flow of positive charges. This convention can be traced back to Ben Franklin, to before people knew whether current in wires consisted of flowing positive charges or flowing negative charges. The fact that we've got things backwards generally doesn't matter, because in most cases positive charges flowing one direction is equivalent to negative charges flowing in the opposite direction.