The difference is the back-light of the monitors. While the technology of the displays of LCD’s and LED’s is basically the same, the LCD monitor uses cold cathode fluorescent lamps as back-lights as compared to the LED monitors that emit diodes. While this is not the only difference between the two, this is the main difference, and a major point of contention between those who prefer LCD technology and those who prefer LED technology.
Since LED’s are built on LCD technology, they have taken this process (manipulating light as it traverses polarized liquid crystals) and have enhanced it, making a higher quality backlight that distinctly affects the quality of the monitor’s display.
This means that LED monitors offer more intense lighting and finer color resolution, meaning that the colors of an LED monitor come closer to the colors one will find in nature. There is also the topic of contrast – LED has a sharper contrast which makes it an excellent choice for those who enjoy quality color and picture reproduction.
Sorry for the long explanation. Hope this helps