Active Matrix
Backlight:
When the backlight shines through the liquid crystal display, the liquid crystals alternately block the light or let it through, which creates the image on the screen. For that reason, you'll need to beware of ultra-cheap LCD computer monitors because the backlights might not be evenly distributed, resulting in a brighter picture in only one spot on the monitor.
Polarizing Layers:
The light from the backlight passes through a polarizing layer, and it will pass through a second polarizing layer after passing through the rest of the display. The polarizing layers are arranged at a 90-degree angle, which means the light won't show through the screen unless the liquid crystals react to change the direction of the light so that it passes through the second polarizing layer.
Transistors:
A glass plate with transistors helps carry the electrical current to the liquid crystals, which prompts them to react and either block or show light.
Liquid Crystals: "LCD" stands for "liquid crystal display," and these crystals are the material that reacts to the electrical current, helping to create the image that you see. The crystals twist and untwist, and this action is what lets the light through.
Color Filter:
The crystals may block and unblock the backlight, but the screen is also composed of tiny filters-one red, one green and one blue-that create the colors you see. Each set of these three filters makes up a pixel. The transistors are associated with the pixels, and if a transistor ever burns out, the liquid crystal won't be able to react, which results in a "dead pixel."
A single-pixel LCD structure;
The sandwiched liquid crystal layer (typically on the order of 5 microns in thickness, or 1/20 of the width of human hair) is straddled by a pair of optical filters with orthogonal polarizations. When no voltage is applied across the crystal layer, incoming unpolarized light gets polarized as it passes through the entrance polarizer, then rotates by 900 as it follows the molecular spiral, and finally emerges from the exit polarizer, giving the exited surface a bright appearance. A useful feature of nematic liquid crystals is that their spiral untwists under the influence of electric field (induced by a voltage difference across the layer). The degree of untwisting depends on the strength of the electric field. With no spiral to rotate the wave polarization as the light travels through the crystal, the light polarization will be orthogonal to that of the exit polarizer, allowing no light passes through it. Hence, the pixel will exhibit a dark appearance.
The energy needed for the electron beam means that the monitors consumer and generate a lot more heat than the LCD monitors.
Pros:
Cons:
LCDs
Advantages
Size and weight:
As was mentioned earlier, the size and weight of an LCD monitor can be upwards of 80% lighter than an equivalent dimension CRT screen. This makes it possible to users to have larger screens for their computers than was possible before.
Produce less eye fatigue:
The constant light barrage and scan lines of a CRT tube tend to cause strain on heavy computer users. The lower intensity of the LCD monitors coupled with their constant screen display of pixels being on or off produces less fatigue for the user.
Disadvantages
Fixed or native resolution:
An LCD screen can only display the number of pixels in its matrix and no more or less. It can display a lower resolution in one of two ways. Using only a fraction of the total pixels on the display or through extrapolation. Extrapolation is a method whereby the monitor blends multiple pixels together to simulate a single smaller pixel. This can often lead to a blurry or fuzzy image particularly with text when running the screen below is native resolution.
Lower response times:
This has been overcome by many improvements, but there are some that still have low response times. Purchasers should be aware of this when purchasing a monitor. However, the improvements are often work arounds that can actually lead to another problem of reduced color clarity. Unfortunately, the industry is very poor about properly listing the specifications for monitors to help buyers understand and compare monitors.
Pros:
Cons:
Light movement
2. Online (voltage is applied)
Molecules movement 
Physical principle
Liquid crystals are neither a pure solid nor a pure liquid, but rather a hybrid of both. One particular variety of interest is the twisted nematic liquid crystal whose molecules have a natural tendency to assume a twisted spiral structure when the material is sandwiched between finely grooved glass substrates with orthogonal orientation. Note that the molecules in contact with the grooved surfaces align themselves in parallel along the grooves. The molecular spiral causes the crystal to behave like a wave polarizer; unpolarized light incident upon the entrance substrate follows the orientation of the spiral, emerging through the exit substrate with its polarization (direction of electric field) parallel to the groove’s direction.
