Speaker cables connect the outputs of the power amplifier or the amplifier section of the receiver to the speaker. These cables carry the high-powered electrical currents required to move the internal components of the speaker.
You need one pair of speaker cables for each speaker in your home theater (except the subwoofer, if it’s an active system that uses an analog audio interconnect cable). Some expensive speaker systems can use two pairs of speaker wires per speaker.
Because they typically go for longer distances (especially in the case of surround speakers) and carry more electrical current than interconnects, speaker cables are considerably thicker than interconnects. The thickness of speaker cables is referred to as gauge.