Feb 21, 2005
A very informative article by Rojas at Engadget:
First, to be technical, there are eighteen different ‘ATSC DTV (digital television) formats’ of which only six are actually High-Definition. Of the six HDTV formats only two are used frequently, 720p and 1080i.
Rojas then goes on to explain the difference between 720p and 1080i.