Only Related to LED-lid LCD TVs.
More recent flat panel TVs use small LED (Light-emitting diode) backlighting to improve the problems with contrast. There are three main types of LED backlighting used in current LCD panels:
1) Edge-lit: Strips of LEDs lightning along one or more edges (sides, and/or top-bottom) of the display, using a special guide to spread the light evenly across the screen.
Pros: Allows for ultra-thin TVs
Cons: Edge lit screens can have problems with light visibly leaking from the edge of the screen, mostly a concern for the lower end LED TVs.
2) Direct-lit: A grid of LEDs across the back of the display.
Pros: Lower manufacturing costs
Cons: LEDs cannot be independently dimmed, which can limit picture contrast. Thicker TVs than edge-lit.
3) Full Array with local dimming: Similar to Direct-lit, a grid of LEDs across the back of the display, but with much higher number of LEDs which can be intelligently dimmed for darker areas of the screen and be bright when necessary
Pros: Golden standard for LCD backlighting, exceptional contrast generated by local dimming technology.
Cons: More expensive. Thicker than edge-lit TVs.