A refrigerant is a substance used in cooling systems, such as air conditioners and refrigerators, to absorb and release heat. It changes from a liquid to a gas and back again, allowing it to transfer heat from one area to another. This process is essential for maintaining a comfortable indoor temperature and preserving food. Refrigerants come in various types, including hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), each with different properties and environmental impacts. Some refrigerants are being phased out due to their potential to harm the ozone layer or contribute to global warming.