Speaker wire is a general term for the wire used to connect loudspeakers to a radio, amplifier, television or other audio source. Most speaker wire is two-conductor copper or silver wire in flat neutral-colored plastic insulation.
Audio speakers produce sound by converting electrical signals to mechanical energy, which vibrates a cone made of paper or other thin material. These electrical signals move from the audio source to the speaker through the speaker wires, making them electrical conductors.
Speaker wire, like other electrical conductors, is described by its gauge. Gauge is a measure of the wire diameter. The lower the gauge, the thicker the wire. Thickness also controls the level of current a wire can safely transmit. Speaker wire is usually 14- or 16-gauge wire, the same as the cord used for lamps and other low-wattage electrical appliances.
Copper is an excellent conductor of electricity, though other metals are better. Copper is used in household applications because it has very good conductivity and is inexpensive. High-end speaker wire uses metals and alloys with higher conductivity to improve audio reproduction and may also have special insulation and sheathing to prevent electrical interference. This expensive construction is wasted in ordinary electrical use, but inexpensive speaker cable is a little different from lamp cord of the same gauge and can be used in similar settings.