This article talks about how refrigeration systems work and the coolants they use to keep things cold, like in fridges and freezers. It covers different types of refrigerators for homes, shops, warehouses, and transporting goods. The article explains the parts that are common in all fridges and then talks about special designs for each type. It mentions that choosing the right coolant is important because some can harm the environment by damaging the ozone layer and causing global warming. It also discusses how the oil that helps the fridge's compressor work can be affected by new coolants.