Short answers, pulled from the story.
A joke is a display of humour in which words are arranged within a specific, well-defined narrative structure to make people laugh, and is usually not meant to be taken literally. It typically takes the form of a short story with dialogue that ends in a punchline, where the humorous element is revealed. The linguist Robert Hetzron emphasised that the tension must reach its highest level at the very end, with no continuation to relieve it.
The oldest identified joke is an ancient Sumerian proverb from 1900 BC containing toilet humour: "Something which has never occurred since time immemorial; a young woman did not fart in her husband's lap." Its records date to the Old Babylonian period, and the joke may go back as far as 2300 BC. The second oldest, found on the Westcar Papyrus and believed to be about Sneferu, comes from Ancient Egypt around 1600 BC.
According to Victor Raskin's Script-based Semantic Theory of Humour, a trigger in the punchline causes the audience to abruptly shift from the obvious interpretation of the story to a second, opposing one. The two interpretations must both fit the joke text yet be incompatible with each other. The psychologist Thomas R. Shultz described this as two stages of incongruity, perception followed by resolution, and that resolution generates laughter.
The Philogelos, Greek for The Laughter-Lover, is the earliest surviving joke book, a collection of 265 jokes written in crude ancient Greek dating to the fourth or fifth century AD. The classicist Mary Beard suggests it may have been a jokester's handbook of quips to use on the fly rather than a book read straight through. One of its jokes resembles Monty Python's "Dead Parrot Sketch."
A joke cycle is a collection of jokes about a single target or situation that shares a consistent narrative structure and type of humour. Well-known examples include elephant jokes using nonsense humour, dead baby jokes using black humour, and light bulb jokes about operational stupidity. Cycles also attach to catastrophes such as the death of Diana, Princess of Wales, the death of Michael Jackson, and the Space Shuttle Challenger disaster.
Jokes are studied across psychology, linguistics, folklore, anthropology, the physiology of laughter, and computational humour. Sigmund Freud treated jokes seriously in his 1905 work "Jokes and their Relation to the Unconscious," while Victor Raskin and Salvatore Attardo developed the General Theory of Verbal Humour as a linguistic classification system. The field requires a multidisciplinary, interdisciplinary, and cross-disciplinary approach to grasp the joke fully.