HD DVD — HD DVD is a new standard for next-generation optical systems that delivers brilliant, high-definition performance. DVD and HD DVD share the same basic disc structure. In addition to DVD's MPEG-2, HD DVD players also recognize both MPEG-4 AVC and VC-1 based on Microsoft's Windows Media.
HDTV — High-Definition Television, a new type of television that provides much better resolution than current televisions based on the NTSC standard. HDTV is a digital TV broadcasting format where the broadcast transmits widescreen pictures with more detail and quality than found in a standard analog television, or other digital television formats. HDTV is a type of Digital Television (DTV) broadcast, and is considered to be the best quality DTV format available.