LCD stands for "liquid crystal display" and technically, both LED and LCD TVs are liquid crystal displays. The fundamental technology is exactly the same in that both television kinds have two layers of glass that is polarized by which light is both blocked and pass by the liquid crystals. So actually, LED displays really are a subset of LCD screens.
Two layers of crystalline material with both polarising layers and arrays of electrodes printed on to them, using a layer or film of "liquid crystal" stuff inbetween.
The electrodes form a grid arranged so the voltage across each section or pixel region on the screen can be controlled. Altering the voltage on the other side of the liquid crystal material causes the optical polarisation of it's to alter, enabling less light through depending on the way that it aligns with all the polarisation that is fixed or more layers.
Simple LCDs have the connections brought out to the border of the panel as well as the control electronics is not internal.
Larger & rapid response ones have active circuitry built-in to the panel itself (thin film transistors) to independently control each pixel.
The LCD has some type of illumination, either cold or LED -cathode fluorescent tubes, to supply the light for the image. (A "LED" display TV or monitor is an LCD using an LED backlight).
They need external light to generate a visible image since LCD panels create no light of their own. In a "transmissive" kind of LCD, this light is provided at the back of the glass "stack" and is called the backlight. While passive-matrix displays are usually not backlit (e.g. calculators, wristwatches), active-matrix screens virtually always are.
But the actual increase to LCD production technology may come from most of the cash that businesses are pouring to the development and research procedure on big display, AMLCD screens for the long-awaited high-definition television technology.