Tornado Alley (PROG)

[BullNBear52]

The signal; is going from analog to digital. Which is why if you don't have cable you'll need a converter box.

That said the HD part is just better resolution/pixels of the picture. Similar to computer monitors.

Resolution is the main reason why HDTV looks so much better than standard television. On a high-def TV displaying a high-def source, a million or more pixels combine to create images that appear sharper and more realistic than TV ever has before. Resolution isn't the be-all and end-all of picture quality, however, and its numerous, well, numbers, can be incredibly intimidating at first. In this article we'll try to demystify HDTV resolution and help you cut through the hype that surrounds all of those numbers.

http://www.cnet.com/1990-7874_1-5137915-1.html