Liquid Crystal Display (LCD)
LCD televisions are flat-panel displays that work by controlling the amount and intensity of light that passes through its screen. They consist of two, perpendicularly arranged panes of polarized glass "stuck together" by a liquid-crystal-filled polymer solution. When exposed to electrical currents, these liquid crystals untwist to varying degrees, thus permitting specific amounts (and colors) of light to pass though them.
When the backlight shines on to the first layer, it filters the light, which then hits the layer of liquid crystal. This contains thousands of blobs of liquid crystal in tiny containers called cells. A trio of these cells makes up one pixel on the screen and each cell has a red, green or blue filter in front of it.
The cells are capable of twisting the light that passes through them- if not the second filter would block all the light. Varying the voltage applied to each cell controls the twist and consequently the amount of light that each one passes through the second filter.
This alters the brightness of each pixel on the screen and, by varying the mix of red, blue and green, the colour. Every single one of the thousands of pixels that make up the screen is controlled in this way to build up the complete picture that you see when you watch TV.
LCDs are projection TVs that depend on a super-bright lamp as their light source, so they're a passive display technology.