Burping is, probably, most commonly air. If someone eats or drinks quickly, talks a lot when eating, has weak muscular control of the throat and poor swallowing ability – excessive air is likely to be taken in and an air bubble forms that someone may intentionally or unintentionally burp up. Sometimes, the air just dissolves and passes down. However, if burping or belching is excessive and/or new (especially in an adult), it can be the result of the body having difficulty digesting the food. Again, in an adult, it frequently is a sign that the body might need more HCl (hydrochloric acid, produced in the stomach and necessary for protein digestion).