Plasma displays use an entirely different principle to produce their images. Each individual dot (“pixel”) on a plasma screen behaves like three fluorescent light bulbs (one for each of red, green, and blue): Gases inside tiny glass cells are excited electrically to form a “plasma”, which then discharges, causing light-producing chemicals (“phosphors”) to emit the colored light that the viewer sees.
Since the light is produced by the cells themselves, plasma TVs use no backlight – if a part of the picture is black, the screen simply doesn’t produce light in that area. Blacks are therefore much, much darker than on traditional LCDs.
One advantage is that each cell behaves like a tiny light bulb, emitting light in all directions, so the picture quality varies little when the screen is viewed from one side. The main benefit of a plasma TV is its more contrast-rich picture.
The lack of a backlight also means there’s none of the blurring that LCDs suffer – plasma pixels flash like a strobe light anyway, producing the same effect as the pulsed backlights now being used in LCDs. The downside is that, overall, plasma technology produces less light than LCDs – and even while using more energy. This low light-output is why plasmas work best in dark rooms.