Yes, I actually looked this up. Idleness is educational.
Flatulence, presence of excessive amounts of gas in the stomach or intestines. Most of the gas in the stomach consists of atmospheric nitrogen and oxygen that have been swallowed. The nitrogen is largely unabsorbable and travels on through the intestines. Additional gases, principally carbon dioxide, methane, and hydrogen, are formed within the intestines. The carbon dioxide, produced by fermentation, is largely absorbed. The other gases, produced by incomplete digestion of foods rich in starch or cellulose, such as beans or cabbage, are eventually expelled from the rectum as flatus. The disagreeable odor of flatus is caused by several sulfur compounds, particularly by mercaptans. Large amounts of gas in the stomach or intestines may cause distention and pain.
Farts. Nature's happy asshole laughter.