Let's start with audio-only cables. The most common audio cables are called analog RCA cables. These are the cables with red and white, or sometimes red and black connectors. RCA cables are widely used to connect devices like VCRs and DVD players to TV sets or CD players to stereo receivers. RCA audio cables come in pairs with two connectors on each end, a red one for right stereo and a white (or black) connector for left stereo. They are often bundled with video cables. Experts recommend gold-plated RCA connectors for extra protection against corrosion, especially if you live in a humid environment [source: Graves].
The other most common type of audio cable is speaker wire. Speaker wire runs from a stereo receiver to all speakers except the subwoofer (that requires a coaxial cable). Each speaker needs its own dedicated wire. Speakers not only receive audio signals via speaker wire, but also power.
Speaker wire is made from 99 percent oxygen-free copper and usually comes "unshielded," which means you can see the copper conductor. Speaker wire comes in different thicknesses or gauges rated from 12 to 18 (thickest to thinnest). As a general rule, the longer your speaker wire, the thicker the gauge you should use. For speaker wire lengths up to 20 feet (6.1 meters) long, 14-gauge is sufficient, but anything longer than 60 feet (18.3 meters) requires 12-gauge wire [source: ecoustics.com].
Speaker wire is fairly simple, so you can get away with buying inexpensive, bulk wire. And don't let anyone tell you that all of the speaker wires in your system need to be the same length. That's a myth [source: Cobalt Cable].
Most audio recordings are digital nowadays, and there are several newer cables that specialize in carrying high-bandwidth digital audio signals. Optical digital cable (also known as fiber-optic and Toslink) transmits audio signals as pulses of light and is impervious to interference [source: ecoustics.com]. Another digital audio cable is called digital coaxial. It looks the old coaxial cables that connect satellite dishes or cable TV signals to televisions, except this is specially designed to carry digital audio. You'll find optical and digital coaxial jacks on newer DVD players, CD players and stereo receivers.
The last type of audio-only cable is called analog multi-channel cable. This cable is designed for use with special players such as DVD-audio that play discs recorded at high sample rates for the maximum sound quality. Analog multi-channel cable consists of six to eight bundled RCA connectors, each responsible for a different audio channel on the back of a stereo receiver.
Next we'll talk about video-only cables, a slightly more complicated topic.