Am i the only one who can use google?
"How does DVI work?
To understand how DVI works we must first understand how a PC creates and transmits a video signal. PC's create digital signals (0's and 1's)
Many people are now moving up from old style CRT technology to small and nice looking LCD monitors. One thing they may not know is that although all LCDs are digital, not all LCD monitors have a DVI connection. Without a DVI connection image quality is diminished because the video card on your PC has to turn the signals into analog and the LCD has to convert them back to digital when it receives them. (An LCD monitor without a direct DVI connection still has a graphics interpreter in the monitor itself to convert those analog signals back into digital.) In basic terms that 1 could end up looking like either a 0.935 or 1.062 to an LCD monitor, no difference in image quality yet you spent all that money on a good flat panel LCD. What a waste, huh?
This is where DVI comes in. Most video cards now-a-days have DVI ports built into them as well as the normal VGA connection. This is where I explain the usefulness of them. It makes no sense to convert digital signals into analog just to be forced to convert it back to digital form once more at the display. The loss of image quality between non-DVI LCD's and DVI LCD's is minimal at lower resolutions, but at higher ones, you'll start to notice quickly. DVI allows this loss to be virtually non-existent. There are many different ways to implement the DVI specification too, all the way from just buying an LCD with DVI or implementing the cables into your system set up."