well, to keep things simple:
any standard analog tv can receive up to 480i. (i is for interlaced, p is for progressive) hd-compatible tv's can accept 480p, 720p (depending on the tv), and 1080i. the number (ie 480, etc) represents the number of lines drawn on the screen in one cycle. generally, the more lines, the better the picture. 480p is used by dvd players mostly, although FOX does broadcast in 480p as well. 720p is a very high-quality picture, and some even prefer it to 1080i, since it's progressive, but few tv's supported it, and the hd industry has all but dropped in in favor of 1080i, which is what a good 90% of all hd broadcasts are.
this will help you understand interlaced vs. progressive:
http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html?KeohiHDTV
good luck
any standard analog tv can receive up to 480i. (i is for interlaced, p is for progressive) hd-compatible tv's can accept 480p, 720p (depending on the tv), and 1080i. the number (ie 480, etc) represents the number of lines drawn on the screen in one cycle. generally, the more lines, the better the picture. 480p is used by dvd players mostly, although FOX does broadcast in 480p as well. 720p is a very high-quality picture, and some even prefer it to 1080i, since it's progressive, but few tv's supported it, and the hd industry has all but dropped in in favor of 1080i, which is what a good 90% of all hd broadcasts are.
this will help you understand interlaced vs. progressive:
http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html?KeohiHDTV
good luck