The easiest I've seen it explained is like a water pipe that represents the flow of electrons in an electrical circuit. The pressure in the pipe is voltage (volts), the flow through the pipe is current (ampere), and resistance (ohms) is the size of the pipe. Opening the valve of a water pipe is like turning on a light switch. You start flow through the circuit. The faster the flow (ampere), the lower the pressure (voltage), while the pipe size (ohms) remains constant.