Help with car audio ohms.?

Kind of a hard thing to explain to someone... An OHM is a measure of impedance. It measures the resistance to the flow of power thru a device. The reason it's important to know what that measurement is for amps & speakers is the two components must match. The amp & the speaker(s) should be the same OHM valve for them to best work together. Impedance is additive, so if you take two speakers, each 4 OHMS, & wire them in series, so the power goes thru one speaker & then the second one, the amp will only 'see' 2 OHMS. So, basics, the amp & the speakers should both be the same. Some amps give you different output taps of different OHMS, so there could be a set of output taps for 4 OHMS & a separate set of output taps for 2 OHMS.