Current that reverses its direction of flow periodically (Hz).
AC is short for alternating current. This means that the direction of current flowing in a circuit is constantly being reversed back and forth. This is done with any type of AC current/voltage source.
The electrical current in houses is alternating current. It comes from power plants that are operated by the electric company. The big wires stretching across the countryside carry AC current from the power plants to the loads, which are in homes and businesses. The direction of current switches back and forth 60 times each second.