Natural refrigerants are substances that occur naturally in the environment, such as carbon dioxide, ammonia, and hydrocarbons. They have negligible environmental impact, with zero ODP and low GWP. In contrast, synthetic refrigerants like CFCs, HCFCs, and HFCs are man-made and have significant environmental implications. Natural refrigerants are gaining popularity due to their eco-friendly profile, but they often require specialized equipment and handling procedures.