Standard Definition TV (SDTV) - SDTV is the basic level of quality display and resolution for both analog and digital. Transmission of SDTV may be in either the traditional (4:3) or widescreen (16:9) format. SDTV's maximum resolution is expressed as "480i" (480 interlaced lines of vertical resolution).
Enhanced Definition TV (EDTV) - EDTV is a step up from SDTV. EDTV offers the traditional (4:3) format or in a widescreen (16:9) format, and provides better picture quality than SDTV, but not as high as HDTV. EDTV's maximum resolution is expressed as "480p" (480 progressive scan lines of vertical resolution).
High Definition TV (HDTV) - HDTV provides the highest resolution and picture quality of all digital broadcast formats. HDTV has several levels of quality expressed in their maximum lines of resolution. HDTV can be filmed in both the traditional (4:3) format and a widescreen (16:9) format. Combined with digitally enhanced sound (Dolby 5.1) technology, HDTV sets new standards for sound and picture quality in television. HDTV's available resolutions are expressed as "1080i" (1080 interlaced lines of vertical resolution), and "480p" or "720p" (480 or 720 progressive scan lines of vertical resolution). The higher the number, the better the resolution, so even though "Progressive scan" technology provides a higher quality picture than "interlaced", 1080i still results in higher resolution.
Full High Definition TV (Full HD) - HDT provides the highest resolution and picture quality of all digital broadcast formats. HDTV has several levels of quality expressed in their maximum lines of resolution. HDTV can be filmed in both the traditional (4:3) format and a widescreen (16:9) format. Combined with digitally enhanced sound (Dolby 5.1) technology, HDTV sets new standards for sound and picture quality in television. HDTV's available resolutions are expressed as "1080i" (1080 interlaced lines of vertical resolution), and "480p", "720p", and "1080p" (480, 720, or 1080 progressive scan lines of vertical resolution). The higher the number, the better the resolution, and "progressive scan" is far superior to "interlaced". "1080p", the highest resolution possible, is thus "full HD" or "true HD".
NOTES: HDTV and digital TV are not the same thing... HDTV is a subset of digital TV. Widescreen cameras are heavier, bulkier, and more costly than standard high definition cameras, thus are practical for filming television shows such as CBS's The Amazing Race.