Edge-lit vs. Back-lit
In LED technology there are two ways screen can be illuminated. They can be edge or back lit. They are pretty much self explanatory, but offer slightly different features.
Back-lit TV’s have LED’s placed directly behind the screen. This will allow TV’s to have much better contrast ratio and deeper colors. However the side effect is that the TV’s are generally deeper that Edge-lit TV’s
As you gathered from last sentence Edge-lit LED TV’s are much thinner. Some even few millimeters thin, however since this light source is located on the side of the TV you will not be able to get as rich and deep colors as Back-lit TV’s.
Most LED’s are Edge-lit these days and still offer superior contrast and color to most LCD and Plasma based HDTV technologies. They are also cheaper than Back-lit LED’s.