Same as S-video. The video signal components (chrominance and luminance,) horizontal sync and vertical sync sent between devices on individual wires as compared to composite video where all the signals are sent on a single wire. The S-video advantage is higher video quality because it does not go through the combining and separating process needed with composite video.
Y/C Video separates luminance (Y) and chrominance (C) for better image quality than composite video. Though outdated, it was used in older CCTV systems for improved analog signal clarity.