| Electric current is the continuous flow of electrons through a conducting material (like a copper wire). Electrons are invisible so to understand the basics of how circuits work, it helps to examine a mechanical system that behaves in many ways similar to the electric circuit.
This mechanical system consists of a pump pushing water through a closed pipe. If we imagine that the electrical current is similar to the water flowing through the pipe, then the following parts of the two systems are related:
The power in the circuit is given by the product of the voltage and the current. The same power can be carried by a high voltage and a low current as is carried by a low voltage and a high current. The higher the current flow however, the more energy is lost through heating the wires when traversing the circuit. That's why high voltage and low current is used when transporting electrical energy along power lines.