Hydrochloric acid (HCl) is a strong, colorless acid that is commonly found in laboratories and industrial settings. It is formed when hydrogen chloride gas dissolves in water. HCl is highly corrosive and can react with various materials, making it useful for cleaning metals and adjusting pH levels in solutions. In the human body, hydrochloric acid is produced in the stomach to aid in digestion. It helps break down food and kill harmful bacteria. Due to its strong acidic nature, HCl is also used in the production of various chemicals and in processes like metal refining and food processing.