A burp (sometimes called a belch or by its medical term, eructation) is the release of gas from the digestive tract (in this case, theesophagus and stomach) through the mouth. It is part of the body natural clearing mechanism for removing excessive gas in the digestive tract (gastrointestinal tract).
There are number of different factors that causes burping or belching. The most common one is the swallowing of air while eating or drinking. When you eat or drink, you swallow air at the same time as you swallow your food or liquid. The trapped air (gases such as nitrogen and oxygen) in the stomach build up and rise to the upper stomach creating a pressure in surrounding area thus, causing a sensation of the need to belch. This excessive gas accumulation is then forced (regurgitated) out of the stomach and released (belched) back up for relief through the esophagus and eventually through the mouth as a burp. Interestingly, burping can be caused by swallowing air (aerophagia) when one is nervous or anxious and even unconsciously out of habit. Drinking carbonated beverages (e.g. sodas, beer and champagne containing carbon dioxide to make it fizzy), talking while eating, eating too fast, chewing gum, sucking through a straw, sucking candy, chewing tobacco, smoking a pipe or cigarettes as well as, eating onions, chocolates and drinking alcohol are some other causes that can cause (trigger or aggravate) belching. Burping (belching) can sometime be a symptom of indigestion.
Burping can also be caused intentionally from being humorous or through learned behaviors. It can be done intentionally out of entertainment of being humorous by children and some adults alike. In some eastern cultures, a belch after a good meal is considered to be a compliment for the chef. It is as a sign showing appreciation of a satisfied eater. However, in the Western world, burping out loud is considered impolite – rude and poor manners. Therefore, burping quietly and covering ones mouth is important and should be accompanied by saying “excuse me” whether your burp is loud or quiet.