i need english terms of what ohms is

i looked it up  the 12volt, but dont really undertand what ohms is. i know its a measure of resistance, but i need someone to simply put how you calculate this resistance, and what it is. in laymens terms.

thanks.

Resistance is a physical property. You usually measure it with an ohmmeter. You can also measure both current and voltage, however, and calculate impedance by Z = V/I. That's basically how ohmmeters work, anyway - they apply a small voltage across the load to be measured.

Warning: this next part is a little more technical but still pretty dumbed down. You might want to skip it if the above explanation is enough.

Impedance is sqrt(resistance^2 + reactance^2). Resistance is DC. It's what a regular wire or a resistor has. Reactance is caused by AC, typically coils and capacitors. If your inductance (caused by coils) and capacitance are negligable, then you can just assume that impedance equals resistance.

Her's how I used to teach this in very basic introductory classes.  (Engineers and electricians out there can either stop reading now or laugh at the simplicity of this analogy!)

Think of wires as pipes.  Think of electricity as water flowing through those pipes.  If the pipe is bigger, more water can flow than if it is smaller.  The larger pipe has less "resistance" to water flow.  Wires work basically the same way. A wire with less resistance allows more electrical current to flow , and one with more resistance makes it harder for the current to flow.  An ohm is simply a unit of measure for electrical resistance, similar to a dollar being just a unit of measure for monetary value.  More ohms = more resistance = harder for the current to flow.