A traffic film is the term used to describe the fine layer of contaminants that cover a vehicle that has been used. The very film layer of contaminants lie on top of the car as a grey-ish film. Washing alone might not always be enough to fully remove this film.
Paintwork can, in some cases, become oxidized. Making it turn matte and slightly fade color. If untreated, it can eventually cause the lacquer and/or paintwork to completely fail. It is most common on red cars, but it can happen with every color.