That quote BTW isn't my quote it was taken from the fatshark thread bm
High-definition video is video of higher resolution than is standard-definition. While there is no specific meaning for high-definition, generally any video image with more than 480 horizontal lines (North America) or 576 lines (Europe) is considered high-definition
720 scan lines is generally the minimum even though many systems greatly exceed that. Images of standard resolution captured at rates faster than normal (60 frames/second North America, 50 fps Europe), by a high-speed camera may be considered high-definition in some contexts.
The term high definition once described a series of television systems originating from August 1936; however, these systems were only high definition when compared to earlier systems that were based on mechanical systems with as few as 30 lines of resolution. The ongoing competition between companies and nations to create true "HDTV" spanned the entire 20th century, as each new system became more HD than the last.