Exhaust Gas Recirculation is an efficient method used in an internal combustion engine to reduce emissions (NOx). With rapid increase in pollution and growing energy demand, it is needed to incorporate methods to address this environmental problem. EGR works on the principle of recirculation of the exhaust gas back to engine cylinders after processing. This technique of using the waste energy can be implemented to both, petrol and diesel engines. This paper discusses the different EGR techniques and its implementation to various engines. This paper discusses the influence of EGR in current engines to reduce emission. Different methods like Port Fuel Injection and Direct Intelligence Injection is also studied. This paper also shows the different stratification methods for EGR. It was found that the EGR method is more efficient in reducing the emissions.