The "-COOH" group, known as a carboxyl group, is a functional group commonly found in organic compounds. It consists of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group (-OH). This structure makes carboxylic acids acidic, as they can donate a proton (H+) in solution. Carboxylic acids, which contain the -COOH group, are important in various biological and chemical processes. Examples include acetic acid, found in vinegar, and citric acid, present in citrus fruits. These compounds play crucial roles in metabolism and are used in food preservation and flavoring.