In most human cultures, excessive flatulence is regarded as embarrassing and impolite; and hence as a natural subject for humour.
The gases are most often produced by swallowing air, and frequently produced by certain types of food, mostly the fibrous or starchy type and the person's digestive system's reaction to them. The list includes beans, yams, sweet potatoes, chick peas, citrous rinds, chestnuts, broccoli, cabbage, etc. In beans, the most notorious offenders in this regard, the problem seems to arise from starch molecules resistant to digestion: when the ploysaccharides reach the intestines, gut bacteria feed on them, producing gas. In the case of those with [Lactose intolerance]? (ie. most non-Caucasian humans), gut bacteria feeding on lactose can give rise to excessive gas production.
Lactating mothers are instructed to avoid gas producing food in their diet because breastfed babies can vomit when there is too much gas in their stomach.
Methane is the primary gas released; bovine flatulence is one of the primary sources of this [greenhouse gas]?. As methane is flammable, some flatulence is as well.
Colloquial and slang terms for flatulence include fart, passing gas, cut the cheese, etc.