Tarots and Tarotology

The tarot ( first known as trionfi and later as tarocchi, tarock, and others) is a pack of playing cards, used from the mid-15th century in various parts of Europe to play games such as Italian tarocchini and French tarot. In the late 18th century, it began to be used for divination in the form of tarotology/cartomancy.

Like common playing cards, the tarot has four suits (which vary by region: French suits in Northern Europe, Latin suits in Southern Europe, and German suits in Central Europe). 

Each suit has 14 cards, ten cards numbering from one (or Ace) to ten and four face cards (King, Queen, Knight, and Jack/Knave). In addition, the tarot has a separate 21-card trump suit and a single card known as the Fool. Depending on the game, the Fool may act as the top trump or may be played to avoid following suit.

Tarot cards are used throughout much of Europe to play card games. In English-speaking countries, where these games are not played, tarot cards are used primarily for divinatory purposes. 

The Trump cards and the Fool are sometimes called "the major arcana" while the ten pip and four court cards in each suit are called minor arcana. The cards are traced by some occult writers to ancient Egypt or the Kabbalah but there is no documented evidence of such origins or of the usage of tarot for divination before the 18th century.

Tarot card games
The original purpose of tarot cards was to play games, the first rules appearing in the manuscript of Martiano da Tortona before 1425, and the next from the year 1637. 

The game of tarot has many cultural variations. Tarocchini has survived in Bologna and there are still others played in Piedmont and Sicily, but in Italy the game is generally less popular than elsewhere.
The 18th century saw tarot's greatest revival, during which it became the most popular card game in Europe, played everywhere except Ireland and Britain, the Iberian peninsula, and the Ottoman Balkans. French tarot experienced a revival beginning in the 1970s and France has the strongest tarot gaming community. Regional tarot games—often known as tarock, tarok, or tarokk are widely played in central Europe within the borders of the former Austro-Hungarian empire.

• Divinatory, esoteric, and occult tarot

Divination using playing cards is recorded as early as 1540. A manuscript from 1750 (Pratesi Cartomancer) documents rudimentary divinatory meanings for the cards of the tarot. In 1765, Giacomo Casanova wrote in his diary that his Russian mistress frequently used a deck of cards for divination.

• Tarotology 

is the theoretical basis for the reading of Tarot cards, a subset of cartomancy, which is the practice of using cards to gain insight into the past, present or future by posing a question to the cards. 

The reasoning behind this practice ranges from believing the result is guided by a spiritual force, to belief that the cards are instruments used to tap either into a collective unconscious or into the subject's own creative, brainstorming subconscious.
Tarot cards were originally used in games and are still used for that purpose in many parts of Europe.
Tarotology is not considered a science; there is no scientific evidence that readings made from the cards can play a role in making objective predictions about future events.

The main article on Tarot gives full details of the history of Tarot cards as game-playing cards.
https://en.wikipedia.org/wiki/Tarotology