LED Christmas lights are small, colored, light emitting diodes that are linked together by a wire and used to decorate trees, window frames, the roofline of houses, and other items as a way to celebrate the holiday season. Unlike traditional miniature incandescent bulbs, they are illuminated by the movement of electrons in a semi-conductor material rather than heat causing an internal filament to glow. LED lights are very efficient, so they don't produce much heat or waste electricity.
The bulbs in LED Christmas lights are typically available in many different shapes, from the traditional cylinders with pointed tips, to balls and cubes, to special designs that look like pine cones or snowflakes. They also produce deep, pure colors rather than the typical yellow-tinted light from traditional incandescent bulbs. LEDs can be made to mimic the "warm" yellow tones of those lights, however, or the sharper, blue-based "cool" colors.
Most Christmas lights come linked together with several strands of wire, which can be green, white, or another color. In many cases, the wire will have a plug on each end — one that can be inserted into an electrical outlet, and one connector that accepts a plug from another strand so that they can be linked together. Rope lights are also available, which have the lights and wires inside of a plastic tube.
Lights are available with one- or two-piece construction, although the two-piece is more commonly available in stores. In one-piece sets, the individual lights are not removable. Because the entire bulb assembly is sealed together, it's less likely that moisture will get into the strand, damaging it; it also prevents loose connections from turning the lights dark. Individual lights cannot be replaced if they burn out.