* Nail vanish (nail polish) is a cosmetic lacquer that is applied to fingernails or toenails to decorate and protect the nail plate. It comes in a variety of colors, textures, and finishes.
* Nail polish remover (nail varnish remover) is a solvent used to dissolve and remove nail polish from the nails. It typically contains acetone or other solvents like ethyl acetate or methyl ethyl ketone.
Think of it like paint and paint thinner. Nail polish is the "paint" that adds color, and nail polish remover is the "paint thinner" that takes it off.