Its a technique by which future is predicted using some cards.
The reading is based on card selected.

Some schools of occult thought or symbolic study, such as the Hermetic Order of the Golden Dawn, consider the tarot to function as a textbook and mnemonic device for their teachings. This may be one cause of the word arcana being used to describe the two sections of the tarot deck: arcana is the plural form of the Latin word arcanum, meaning "closed" or "secret."

Tarot Reading describes the use of Tarot cards for the purposes of fortune-telling,divination, occultism, mysticism, meditation, introspection, and brainstorming.

Go to this url to know in detail
http://en.wikipedia.org/wiki/Tarot_reading
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