An immersion chiller is a device used in home brewing and cooking to quickly cool down hot liquids, such as wort or stock. It consists of a coiled copper or stainless steel tube that is submerged in the hot liquid. Cold water is then circulated through the coil, absorbing heat and rapidly lowering the temperature of the liquid. This method is efficient and helps prevent contamination, as the chiller can be sanitized before use. Immersion chillers are popular among home brewers and chefs because they significantly reduce cooling time compared to traditional methods, ensuring better flavor and quality in the final product.