S-Video (Super-Video, sometimes referred to as Y/C Video, or component video) is a video signal transmission in which the luminance signal and the chrominance signal are transmitted separately to achieve superior picture clarity. The luminance signal (Y) carries brightness information, which defines the black and white portion, and the chrominance signal (C) carries color information, which defines hue and saturation. Traditional or composite video, the way that video signals have traditionally been transmitted, sends both (along with synchronization data) as one signal.
Television sets are actually designed to display luminance and chrominance signals separately. Composite signals must be separated before they can be displayed. When the signals are sent as a composite, they overlap at a frequency range above 2.1 megahertz (MHz). The overlapping areas are difficult to separate entirely, and the remnants of either signal within the other creates video errors. Vestiges of chrominance data remaining in the luminance data cause a cross-luminance effect that creates a dot structure pattern (this is sometimes referred to as "dot crawl"), and vestiges of luminance data remaining in the chrominance data create "rainbow" effects in detailed patterns called "cross-color". Sending the signals separately, as in S-Video, circumvents this error-prone process.