If you own the actual hardware, physical skins are adhesive overlays used for protection or aesthetic personalization.
"Bring the look and workflow of Pioneer CDJ-350 and DJM-350 to VirtualDJ. This high-fidelity skin offers realistic jog wheels, a full-featured mixer panel, hotcue pads, dedicated loop controls and customizable mappings — perfect for practice or live performance." virtual dj skin pioneer cdj 350 djm 350