According to Wikipedia: The first known documented tarot cards were created between 1430 and 1450 in Milan, Ferrara and Bologna in northern Italy. The original purpose of tarot cards was for playing games, with many cultural variations. The variety of decks in use grows yearly. Most importantly, you don’t have to be a psychic to do a Tarot reading.
The belief in divination associated with Tarot focuses on the prospect that whatever cards are dealt to the participant will be revelatory. Each card possesses a pictogram and title that represents a specific concept or archetype.To learn more, there is an excellent article in HowStuffWorks.