One of the things we ingest when we eat food or drink liquid is gas. Drinking a carbonated beverage, for example, such as soda or beer, ingests gas into the stomach. Given that the density of that gas is lighter than the liquid and the solid we have also ingested, it tends to rise towards the top of the stomach, just below the entrance to the esophagus. We can sometimes feel that pressure after a beverage or meal, and a burp, or belch, is one way in which that gas escapes our bodies.
Also, the digestive process that starts when we eat or drink creates gas sometimes as the food is broken down, adding to the pressure in our stomachs and the tendency to burp.
You'll be glad to know that in some societies, like in parts of Eastern Europe, it is considered a great compliment to burp loudly after a meal.
When we eat food, along with the solids and liquids that we eat and drink a lot of gas also goes into our stomach. This is usually the gas that makes up air which is oxygen and nitrogen. When products like carbonated drinks are consumed a lot of carbon dioxide also goes into the stomach. In many cases the gases that have been swallowed, need to be expelled for many reasons, which could include to make way for the proper digestion of food and to accommodate more food that you are eating. A burp or a belch is the gases in the stomach coming up through the esophagus and going out of the body through the mouth.
Burping, also called belching, is partly involuntary act of expelling excess air or gas in the stomach through mouth. Air enters stomach along with food we eat. Gases may also be released in the stomach by some food or drinks like aerated drink, of may be released during digestion of some food food in the stomach. Too much of air or gases create pressure in the stomach. This can make us feel uncomfortable, give stomachache, or cause pain in other parts of body around the stomach. Burping expels the air in the stomach, and thus give relief from discomfort and pain.