The Emergence of HDTV
You might already know that the USA replaced the current analog interlaced TV system (NTSC) dated from the 1940's by a digital DTV system in February 2009. Curiously enough the idea started as "analog" HDTV until General Instruments proposed an all-digital system in 1990.
The DTV standard is composed of 18 digital formats grouped into two levels of quality, as approved by the ATSC (American Television Systems Committee) in 1995:
1) SD: Standard Definition, with 480i/p (i:interlaced, p:progressive) viewable horizontal lines of vertical resolution (rows counted from top to bottom), each line with up to 704 total pixels of horizontal resolution (counted from left to right), and with an aspect ratio (relation of width to height in units) of 4x3 (as regular TV), or widescreen 16x9.
2) HD: High Definition, with 720p and 1080i/p viewable horizontal lines of vertical resolution (rows counted from top to bottom), each line with respectively 1280 (for 720p) or 1920 (for 1080i/p) total pixels of horizontal resolution (counted from left to right), and only in widescreen 16x9 aspect ratio.
Note that the horizontal lines (rows) are expressed as "vertical" resolution (480, 720, 1080), and the vertical columns made of the aligned pixels on the horizontal lines are expressed as "horizontal" resolution (704, 1280, 1920).
DTV was 15 years in the making before it went on the air in November 1998. HDTV is the quality part of DTV, but its implementation is not mandatory, SD is. Most OTA terrestrial TV stations are already broadcasting DTV in SD and HD widescreen, and consumers are buying HDTV sets at accelerated pace every year.
The Consumer Need
The reason that the HDTV set is so popular is that there will always be a desire in the consumer marketplace for the best of all picture and audio quality and there is nothing better for these qualities. This is somewhat interesting when it was only 20 years ago that HDTV was considered to be the best picture and sound quality that "you will never see." The reason for this was because the cost of HDTV would be too expensive for consumer use.
The belief was that the price would never come down low enough that the HDTV television set would ever be affordable in the consumer marketplace. Needless to say, engineers spent quite a bit of man hours figuring out a way to devise cost effective technology and that is why we have the HDTV television set in retail stores this very day.
The Effect DVD had for HDTV
Most of the 6 million people that bought HDTVs on the first 5 years of the transition (1998-2003) did so NOT to view HD, but rather to enjoy playing widescreen DVDs at 480p or upscaled to 720p or 1080i/p to the native resolution of the digital set. The same DVD played on an analog TV would only show the image as a 480i interlaced scanning.
In addition, an HDTV has the capability to show widescreen DVDs in anamorphic format displaying all the original vertical resolution stored on the disc, while 4x3 analog TVs would show the same DVD letterboxing the image between larger top/bottom bars in order to maintain the wider aspect ratio of the movie, and with less vertical resolution for the image itself.