A catalytic converter is a device used to reduce the emissions from an internal combustion engine (used in most modern day automobiles and vehicles).Catalytic converters are used in exhaust systems to provide a site for the oxidation and reduction of toxic by-products (like nitrogen oxides, carbon monoxide, and hydrocarbons) of fuel into less hazardous substances such as carbon dioxide, water vapor, and nitrogen gas.Note:It converts nitrogen oxide, carbon monoxide & hydrocarbon like harmful products into carbon dioxide, water vapour & nitrogen gas like less harmful products.In catalytic converters, the gases are passed over metal-coated beds that convert harmful chemicals into less harmful ones. These are used in cars to reduce the effects of exhaust fumes on the atmosphere.