A CFC is a chlorofluorocarbon. They all contain carbon, fluorine, chlorine and hydrogen. CFCs are non-flammable and not very toxic. They therefore had a large number of uses. They were used as refrigerants, propellants for aerosols, for generating foamed plastics like expanded polystyrene or polyurethane foam, and as solvents for dry cleaning and for general degreasing purposes.
However CFC's are harmful to the ozone layer in the earth's atmosphere owing to the release of chlorine atoms on exposure to ultraviolet radiation. These chlorine ions would then bond with the many oxygen ions within the ozone cycle creating a huge gap within ozone.