A day set aside for the sole purpose of one person making a fool out of another person; that is what All Fool's Day is.
Because of the fact that All Fool's Day fell on the first day of April, it has taken on the additional name of April Fools Day.
In the Colonial Period, the day was spent by some people in sending others on what was known as a sleeveless errand, a mission to retrieve something that was nonsensical or nonexistant. The modern-day equivalent would be a seasoned factory worker sending a new, very naive, employee to get a "wobble-shaft" or "gum wrench" - things that simply don't exist. The joke on the new employee would be revealed when the person from which the nonsense object was to be retrieved laughed at the new employee's gullibility.
In the 13 April 1769 issue of the Public Advertiser it was noted that: This [making fools on the first of April] is said to have begun from the mistake of Noah sending the dove out of the ark before the water had abated, on the first day of the month among the Hebrews, which answers to our first of April; and to perpetuate the memory of this deliverance, it was thought proper, whoever forgot so remarkable a circumstance, to punish them by sending them upon some sleeveless errand similar to that ineffectual message upon which the bird was sent by the patriarch.
For centuries, the Feast of Huli has been celebrated in India on the 31st of March by sending unsuspecting persons on foolish errands.
All Fools Day was also a time for playing harmless tricks on others. Children found humor in telling an elder that his shoe buckle or lace was undone, or that there was a hole in his jacket. When the older man bent over to inspect his shoe, or pulled his jacket around to search for the hole, the children would erupt into laughter and shouts of "April Fool".
The holiday was celebrated in France during the late 1700s with people made of fools being called Poissons d'Avril or "April Fish". This name found, in English, the equivalent silly mackerel.
In the northern reaches of England and in Scotland, people sent on sleeveless errands on the first day of April were called "April Gouks". The word gouk, variously, gowk was a substitute name for cuckoo. And the name of cuckoo was given to those considered to be fools, so on the first of April, when a person was called the April Gouk, it was suggested that he or she was the April Fool.
As the decades rolled by, the harmless jokes played on innocent bystanders continued to delight people on All Fools Day on the first of April. The words "Kick Me" would be written on paper and a finely executed pat on the back would securely affix the joke on the back of an unsuspecting friend. Bricks would be attached to the inside lining of a silk top hat and laughter would erupt as someone reached down to pick up the hat, finding it much heavier than they expected. When telephones became popular and available to the masses, an April Fool joke played on shopkeepers was for someone to call the shop on the telephone with the question: "Do you have Prince Albert [tobacco] in the can?" When the shopkeeper answered "Yes", the jokester would loudly proclaim: "You better let him out."
The peculiar thing about All Fools Day is that, despite its continuing popularity right up to the present-day, there never has been any sort of feast associated with the day. Most of the holidays that have come down through the ages were based on eating certain foods or participating in a sumptuous feast. But All fools Day has never had a food associated with it; it has always only been about the playing of jokes on one another.