A burp is nothing but gas. When you eat or drink, you don't just swallow food or liquid. You also swallow air at the same time. The air we breathe contains gases, like nitrogen and oxygen. Sometimes when you swallow these gases, they need to get out. That's where burping comes in! Extra gas is forced out of the stomach, up through the esophagus (say: ih-SAH-fuh-gus, the tube for food that connects the back of the throat to the stomach), and out of the mouth as a burp.