Answer Description

LCD screens use a backlight to illuminate the screen's display. A plasma lamp is the coolest toy at the Discovery Center. Seriously, Google it.

Wikipedia

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden For instance: preset words, digits, and seven-segment displays, as in a digital clock, are all good examples of devices with these displays They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements