Carboxylic acids contain the functional group -COOH. The first four members of the homologous series are methanoic acid (HCOOH), ethanoic acid (CH3COOH), propanoic acid (C2H5COOH) and butanoic acid (C3H7COOH). Names end in -oic acid, and the carbon in the -COOH group counts, so ethanoic acid has two carbon atoms. Vinegar contains ethanoic acid.
Carboxylic acids dissolve in water to give acidic solutions with a pH below 7. They react with carbonates, so the mixture fizzes as carbon dioxide gas is given off, and a salt and water form. With sodium carbonate, ethanoic acid makes a salt called sodium ethanoate. The salt name comes from the acid, so propanoic acid would make a propanoate.
Carboxylic acids also react with alcohols, using an acid catalyst, to make an ester and water. Ethanoic acid and ethanol make the ester ethyl ethanoate. Esters have sweet, fruity smells, so they are used in perfumes and food flavourings. You do not need to write balanced equations for these reactions.