A refrigerant is a substance used in cooling systems, such as air conditioners and refrigerators, to absorb and release heat. It circulates through the system, changing from a liquid to a gas and back again, which helps to lower the temperature of the surrounding environment. Common refrigerants include R-134a and R-410A. Refrigerants are essential for maintaining comfortable indoor climates and preserving food. They work by transferring heat from inside a space to the outside, making the interior cooler. The choice of refrigerant can impact energy efficiency and environmental effects, as some have higher global warming potential than others.