Neon wire is a slang term for electroluminescent wire, a special kind of wire that glows brightly when a current is run through it. Neon wire is a fairly recent development, only hitting the market around 2000. It consists of a copper core coated in phosphor, wrapped with two very fine wires surrounding the core in a spiral arrangement, all protected by a thin plastic sheath. When a charge runs through the wire, it causes the phosphor to emit a gorgeous light. Neon wire is very flexible, fairly inexpensive, and comes in all sorts of colors.
Of all the luminous materials that civilization has engineered, neon wire is among the most flexible and amenable to creative applications. Neon wire can be powered by a variety of sources - some models can be powered by either AC or DC. Its power requirements are low enough that people design costumes coated in the wires, with light batteries embedded, and the wires glow brightly for hours on end. Sculptures can be accented by the artistic application of the wire, and programmed to turn on at night, making for a new and beautiful decoration.
Some companies also sell control units to accompany neon wire, permitting the user to program them to turn on and off as desired. The brightness of neon wire varies with its thickness - thicker wire can be greatly more luminous. Despite its name, neon wire contains no neon, and may in fact replace conventional neon lighting in many applications. It contains no glass, making it much safer and more difficult to break. The requisite technology for neon wire has been around some time, but simply has not been implemented until recently.
Neon wire is cool to the touch, making it perfect to add to clothing or use for indoor applications. Companies call the wire neon wire, electroluminescent wire, or simply EL wire depending on their preference. It is sold in virtually unlimited length, and like most products, its cost decreases substantially if bought in bulk. There are even professionals who specialize in creating complex statues and designs out of neon wire, some more than 20 feet in height.