Tarot was first known as Tarocci and Tarok. It's divinatory name is Cartomancy or fortune telling or divination using cards. The origins of Tarot are still debated. Some say they come from Egypt, others say Italy, and others say China (basing it off of I Ching). It is known though that they have been used from the mid fifteenth centrury in various parts of Europe though, to play a card came such as Italian Tarocchini and French Tarot. From the late 18th Century until the present, Tarot has also found use by mystics, occultists and the like, in efforts at divination or as a map of mental and spiritual pathways.
The average tarot deck has approxamitely 78 cards. These cards have 4 suits, or element cards, which correspond to the suits of conventional playing cards. Each of these suits as "pip" cards numbers from Ace to 10 and four "face" cards, for a total of fourteen cards. In addition, the tarot is distinguished by 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 followeing suit.
Pictured card packs were mentioned by Martiano Da Tortona around 1418 and 1425, since in 1418 the painter he mentions, returned to milan while martiano himself died in 1425. He describes a deck of sixteen picture cards with images of the Greek Gods and suits depicting four kinds of birds, not the common suits. However the sicteen cards were obviously regarded as "trumps" as, about twenty-five years later, jacopo Marcello called them a Ludus triumphorum, or "game of trumps."
The Tarot decks of today are associated with mysticism and magic. Tarot was not widely adopted by mystics, occultists and secret societies until the 18 and 19th centuries though. The tradition began around 1781, when Antoine Court de Gebelin, who was a swiss clergymand, published Le Monde Primitif, a speculative study which included religious symbolism and it's survivals in the modern world.De Gebelin first asserted that symbolism of the Tarot de Marseille represented the mysteries of Isis and Thoth (many of you have probably heard about the Thoth tarot deck, here's your reference). Gebelin further claimed that the name "Tarot" came from the Egyptian words Tar, meaning royal, and RO meaning road, and such that it ends up meaning the Royal Road to Wisdom. De Gebelin also asserted that gypsies (nomadic peoples) who were among the first to use cards for divination, were descendants from the Ancient Egyptians ( hence their common name, though by this time it was more popularly used as a sterotype for any nomadic tribe) and had introduced the cards to Europe. Despite all this, the identification of the tarot cards with the Egyptian Book of Thoth was already firmly established in occult practice and continues in modern urban legend to the present day.
Todays Decks are seperated into 2 Arcana, the Major and Minor (arcana meaning secrets so when you break it down it's the greater secrets and lesser secrets)
The Major arcana includes twenty two cards without suits (most commonly): The fool, The Magician, The High Priestess, The Emperess, The Emperor, The Hierophant, The Lovers, The Chariot, Strength, The Hermit, Wheel of Fortune, Justice, The Hanged Man, Death, Temperance, The Devil, The tower, the Star, The Moon, The Sun, Judgement, and the World
(or some variation there of)
The Minor Arcana cosists of 56 cards, divided into four suits of fourteen cards each. 10 numbered cards, and four court cards. The court cards are the King, Queen, Knight, Page/jack, in each of the four suits (there are several variations to this as well). The traditional Italian tarot suits are Swords, Batons/Wands, Coins and cups; in modern tarot decks however, the baton suit is often called wands, rods, or staves, while the coins suit is often called pentacles or disks.
Each tarot deck has it's own symbolism as well, an example of this is the Rider-Waite-Smith Deck which departs from the earlier tarot design with its use of scenic pip cards and the alteration of how the strength and justice cards are ranked.
Now to clear up some cunfusion about Tarot and Oracle Cards. Most recently, the use of tarot for divination, or as a store of symbolism, has inspired the creation of Oracle Card Decks. These are card decks for inspiration or divination containg images of angels, faeries, goddesses, totems, etc. Although Obviously influenced by divinatory tarot, they do not follow the traditional structure. They often lack any suits or numbered cards, and the set of cards differes from the conventional major arcana.
(there is a lot more information out there on this subject, I just condensed a lot of the information. All the information provided came from my book of shadows, and before that varied from a few different websites, ex: wikipedia and the M-W.com )