Electric Calculation

here are already a couple of good answers here (and some others that are WAY off), but I'll see if I can help too.

Voltage is also called "electromotive force." Just think of that key word, "force." It's the force that drives an electric current through a circuit. It is also called "potential" because voltage is a measurement of potential energy.

A lot of times, it's helpful to compare electricity to water. Voltage would be like the water pressure, in PSI, in a garden hose.

Ampere is a measurement of current flow, the amount of electrons that are flowing through a given point in a circuit at any one time. If we compare electricity to water again, Amperes would be like the flow of water in Gallons-per-minute.

Ohms is a measurement of resistance. A higher Ohm rating means more resistance. You can think of resistance as like how narrow a water pipe is. A narrow or clogged water pipe will make it more difficult to pump water. It's kind of the same thing with electric current. Resistance is the opposition to a flow of electricity.

All these terms are used in Ohm's Law. Let's say you have a power supply with 12 volts. Ohm's Law states that Voltage divided by resistance = current. So let's say the circuit has a resistance of 2 Ohms. 12 volts divided by 2 Ohms = 6 Amperes. That will at least give a basic idea of how it fits together.

Watts is a measurement of the TOTAL available power, if we combine Voltage and Amperes. If we use water as an analogy again, you can think of Wattage as sort of like the work being done by a water turbine or wheel. It's the combined effect of the water pressure, and the water flow in GPM. Volts x Amperes = Watts.

This is a simplified explanation, and things get a little bit more complicated when you work with alternating current. But this is the basic idea.