Amperes, amps, or current is the measure of the flow of electricity through a given circuit. It's the (I) in the Ohm's law equation above. Amps are different than voltage in that amps are the same throughout the entire circuit, unlike voltage, which starts out high then drops to zero when it reaches the negative battery post. Amps are the same at the beginning and the end of a circuit. If you have five amps at the beginning of the circuit, you'll have five amps at the end of the circuit.
To continue with our automotive analogy, we'll equate amps to speed. The higher the amps, the faster the speed. The number of amps a circuit uses is dictated by the load and the resistance in the circuit. The bigger the load, the more amps a circuit will use. A starter motor will use a lot more amps than a window motor because the window motor will not need as many amps to run as a starter motor would. This next fact about amps gets a little weird. The lower the resistance in a circuit, the higher the amp flow.
Sticking with our speed analogy, the more amps you have in a circuit, the faster things flow. Remember when I said that if you had a short circuit you'd blow fuses and possibly burn things up? I was taking about amps. If you have unrestricted electron flow with no load, amps get out of control. It's like a speeding locomotive that goes off the track. Something is going to break. With automotive electrical systems, it's usually the weakest link, which should be the fuse. Ever notice how fuses are rated in amps, not voltage? Now you know why.
One last little factoid about amps: You can have high voltage in a circuit and it won’t be that harmful to you. It’ll wake you up for sure, but it won’t kill you. However, if you have just a few amps to go with that high voltage, watch out. As little as 0.2 amps mixed with the right amount of voltage can kill you. In fact, it might even be less than that depending on the circumstances. It’s not the voltage that hurts you; it’s the amps. It doesn’t take too many amps to knock you on your butt, so be extra careful when dealing with amps. To use another common analogy, if volts are pressure, amps are intensity or volume. You can have lots of pressure, but when you add intensity, things can get lively.