As S-VHS is to VHS, so Hi-8 is to Video 8 - it's a higher quality variant of the format that achieves better picture quality by keeping the chrominance and luminance signals separate. Because of its compact size, Hi-8 was a popular camcorder tape format in the early-to-mid 1990s, before being superseded by digital video formats such as Mini-DV.
Found on http://www.screenonline.org.uk/education/glossary.html