Christmas lights, also known as festive lights, are lights used mainly for decoration in celebration of Christmas, often on display throughout the Christmas season including Advent and Christmastide. Christmas lights come in varieties of designs and colors and they have been in use since as early as the 18th century. Some Christmas lights are placed on Christmas trees or house exteriors to celebrate the festive season. Christmas lights can be either incandescent lights or light-emitting diode (LED) lights. Incandescent Christmas lights are the traditional lights that have been used since the 19th century. These lights have a filament inside them that heats up to generate light when current passes through them. LED Christmas lights, however, use a semiconductor to produce light. These lights are much more energy efficient than incandescent lights, and they have a longer lifespan. Christmas lights can be used in a variety of ways to decorate a house or yard. They are often used to create outlines of lights on walls and eaves or hung from trees, shrubs, or gables. Christmas lights can even be hung from rooftops or arranged in creative patterns. In addition to decorating exteriors, Christmas lights can also be used to light up the interior of a home. They are often used on Christmas trees to add a festive, cheerful atmosphere. Christmas lights have become a festive tradition all over the world. They bring light and joy into homes during the dark, cold winters. Whether used to outline a house, as a decoration in the living room, or to dress up a Christmas tree, Christmas lights are sure to bring holiday cheer and unique glamour to any space.