Farting is part of the human condition. We all fart, whether we want to or not.
A fart is produced when gasses trapped in our body force themselves out through our butt.
The gasses are mostly pointless gasses like nitrogen and hydrogen... But a tiny percentage is sulfur. And sulfur stinks.
The vibrations of the rectum produces the distinctive sound of the fart.
Sometimes we swallow air, whenever we eat or drink... Probably when we burp on command, too.
I guess it has nowhere to go but out of one end or the other.
Flatus is the medical word for gas generated in the intestinal tract. Medical literature describes flatulence as "flatus expelled through the anus". (medicalnews.com)
Image sources: 1, screenshot of https://www.google.com/search?client=ubuntu&channel=fs&q=fart&ie=utf-8&oe=utf-8; Information sources: 1, 2
