David Parlett, author of Oxford History of Board Games and A Dictionary of Card Games, writes:
“Tarot, any of a set of cards used in tarot games and in fortune-telling. Tarot decks were invented in Italy in the 1430s by adding to the existing four-suited pack a fifth suit of 21 specially illustrated cards called trionfi (“triumphs”) and an odd card called il matto (“the fool”). (The fool is not the origin of the modern joker, which was invented in the late 19th century as an unsuited jack in the game of euchre.)
The pack to which these cards were added naturally bore Italian suitmarks and belonged to an experimental period of card design when queens were often added to the series of court cards previously consisting of only a king and two male figures (see playing card). In standard cards (but not in tarots), the four figures were subsequently reduced to three again by suppression of the queen, except in French cards, which suppressed the cavalier (knight).
The trionfi each bore a different allegorical illustration instead of a common suitmark. Such illustrations probably represented characters in medieval reenactments of Roman triumphal processions, similar to floats in a modern festival parade. They were originally unnumbered, so that it was necessary to remember what order they went in. Whether or not trionfi were originally produced independently of standard playing cards, their function, when added to the pack, was to act as a suit superior in power to the other four—a suit of triumphs, or “trumps.”
The cards of the major arcana have pictures representing various forces, characters, virtues, and vices. The 22 cards are numbered I through XXI, with the fool being unnumbered. The tarots of the major arcana are, in order, as follows: I juggler, or magician; II papess, or female pope; III empress; IV emperor; V pope; VI lovers; VII chariot; VIII justice; IX hermit; X wheel of fortune; XI strength, or fortitude; XII hanged man; XIII death; XIV temperance; XV devil; XVI lightning-struck tower; XVII star; XVIII moon; XIX sun; XX last judgment; XXI world, or universe; and the fool.
The 56 cards of the minor arcana are divided into four suits of 14 cards each. The suits, which are comparable to those of modern playing cards, are as follows: wands, batons, or rods (clubs); cups (hearts); swords (spades); and coins, pentacles, or disks (diamonds). Each suit has 4 court cards—king, queen, knight, and jack—and 10 numbered cards. In ascending order the value progression in each suit is ace to 10, then jack, knight, queen, and king (though the ace is sometimes assigned a high value, as in modern playing cards).
The adaptation of tarots to occult and fortune-telling purposes first occurred in France about 1780. For fortune-telling each tarot card is ascribed a meaning. The cards of the major arcana refer to spiritual matters and important trends in the questioner’s life. In the minor arcana wands deal mainly with business matters and career ambitions, cups with love, swords with conflict, and coins with money and material comfort. The tarot deck is shuffled by the questioner, and then the fortune-teller lays out a few of the cards (either selected at random by the questioner or dealt off the top of the shuffled deck) in a special pattern called a “spread.” The meaning of any card is modified according to whether it is upside down, its position in the spread, and the meaning of adjacent cards.”