HDTV (High Definition TV)

(High Definition TV) A set of digital television (DTV) standards that offer the highest resolution and sharpest picture. Although a few HDTV sets are available in standard screen sizes, the overwhelming majority are wide screen, which eliminates most or all of the letterbox effect when watching movies in their original format (see image below). See HDTV display modes and high-def DVD formats.
HDTV Vs. HD"HDTV" may refer to the format or to a TV set that supports it; however, "HD" refers only to the high definition format. See DTV for all the SD/ED/HD specifications.
Interlace or Progressive Scan (i or p)The first HDTV sets were available in 720p and 1080i, but not the top 1080p format. The number refers to the lines of resolution, and the letter means the signal is interlaced (i) or progressive scan (p). Many HDTV sets support only 720p, which many think preferable to 1080i for action movies and sports; however, the difference is often subjective. HDTV sets that support 1080p, which began to appear in 2005, ended the argument. See interlace.
Using sophisticated algorithms to fill in the missing lines, HDTV sets upconvert DVD, cable and satellite broadcasts from 480i or 480p to 720p, 1080i or 1080p, whichever HD resolution the TV supports. HDTV sets that support 720p, the lowest HD format, are able to downconvert 1080i material to 720p. Following are all HDTV standards (see DTV for all digital standards).
In addition, HDTV sets provide numerous zoom and stretch modes to accommodate standard TV formats, which will exist in the form of videos and DVDs for years to come (see HDTV display modes).
p = progressive scan (non-interlaced) i = interlaced Frame Resolution Aspect Rate Pixel Horiz x Vert Ratio (fps) Shape
HD - High Definition TV (HDTV) 1. 1920 x 1080 16:9 24p Square 2. 1920 x 1080 16:9 30p Square 3. 1920 x 1080 16:9 30i** Square
4. 1280 x 720 16:9 24p Square 5. 1280 x 720 16:9 30p Square 6. 1280 x 720 16:9 60p** Square
** = most popular formats

HD Ready or Built InAn "HD Ready" or "HD Capable" TV set means it can display 720 progressive lines of resolution (720p) at minimum and can scale up lower and scale down higher-resolution signals to fit the screen. HD Ready requires an HD set-top box from the cable or satellite company to receive HD programs. "HD Built In" means there is a built-in HD tuner for capturing HD broadcasts over the air.
Been Around a WhileSince the turn of the century, consumers have become familiar with high definition TV; however, HD was available years before that. Japan experimented with HD formats in the 1970s and 1980s and was the first to broadcast an 1125-line signal for very expensive, large-screen TV sets in the early 1990s. Both Japan and Europe's initial HD formats were analog.
For many years in the U.S., various HD formats in both analog and digital were used for creating higher-quality video than regular TV (NTSC). HD was used to shoot closed circuit presentations in corporate theaters and board rooms, trade shows and similar events. See interlace, deinterlace, DTV, letterbox, HD-DVD and aspect ratio.

Wide Screen HDTVWhen a movie shot for a theater is displayed without modification on a standard 4:3 TV screen, the black lines at the top and bottom take up the unused space (the "letterbox" effect). Since almost all HDTVs have wide screens with a 16:9 aspect ratio, movies can be shown in their original format.
Now, if you were looking for buyer's guide here are few links :-)
http://www.hdtvorg.co.uk/guide/hdtv/buy_guide_hdtv.htm
http://www.brightandsleek.com/Articles.asp?ID=109