HDTV refers to High Definition Television. In the most basic of terms it refers to a picture which has 720p or 1080i or 1080p performance. 480p is considered Improved Definition TV. When selecting an HDTV do not compare specs as, once again, they are misleading and the bad manufacturers always stretch the truth. Do not use numbers like 120 or 240 Hz. to judge. Do not go to the store and look at pictures (but we all do) because the sets can be preset so differently to favor one set over the next. Do not pick the brightest TV. Instead look for great blacks in the pictures, natural colors and, most importantly, look for a TV that does not turn to a digital blocking out of focus mess picture during sporting events due to its inability to process the video fast enough. Do read up from the experts like Consumer Reports. Do pick a brand with known great reliability.