It was around 1990s that the Digital HDTV Grand Alliance initiated this technic in the US. Specifically it is said to carry 1080 active lines, 16 x 9 specific proportion in ITU-R BT.709.
High defintion television means broadcast of big screen images with more refinement and clarity than seen in regular analogue TVs, or another modern TVs formats. No one can strive this Digital Television broadcast format in sharpness as it is undoubtedly the highest.
High defintion TV is available in plasma, direct-view, rear screen, and front screen projection. HDTVs can be seen only through HDTV tuner and 1080i is the most definite HDTV format.