High-definition video facts for kids
High-definition video (HDTV Video or HD video) is video of higher resolution and quality than standard-definition. While there is no standardized meaning for high-definition, generally any video image with considerably more than 480 vertical scan lines (North America) or 576 vertical lines (Europe) is considered high-definition.
480 scan lines is generally the minimum even though the majority of systems greatly pass that.
High-definition video Facts for Kids. Kiddle Encyclopedia.