Ohms is a rating that refers to the restriction of power, or impedance. The higher the ohm rating, the more impedance is applied to the flow of power. Most home receivers and speakers are rated 4, 6 or 8 ohms. The exact rating can be found on the unit. When matching speakers and Audio/Video (A/V) receivers, the ohm rating of the speaker should be equal to or greater than the ohm rating of the receiver.
WARNING: There is a risk of hardware damage. Matching speakers with lower impedance than what the A/V receiver is rated may cause damage to the receiver and is not recommended.
NOTE: Some receivers have an impedance range, others may have an impedance switch. The switch may allow lower impedance speakers to be connected without harm to the receiver as long as the switch is set to the correct impedance.