The origins of the cards are much debated. Although the first tarot decks as we know them appeared in the 15th century, the concept behind them is as ancient as civilization. Humans have the distinct ability to observe synchronicities, or patterns of occurences, and how these occurences relate to one another. For example, the ancient Chaldeans observed how human behavior, or the personality of a new-born, coincided or synchronized with the positions of the stars. Over time, these synchronizations became predictable patterns, i.e. Venus, 'the bright star', when closest to the Moon, coincided with events and births that were notably pleasant, positive, generous, kind, and good natured. In other words, events could be 'divined' by careful observance of signs in nature.
Tarot, then, or any system of divination, is based upon this phenomenom of synchronicity. The cards that fall or are drawn at a specific moment in time will reflect the energy of the questioner. A Tarot reader is adept at reading the cards as symbols of energy and as symbols of how that energy will unfold. Though it is not easy to change one's energetic patterns, it is possible. When the mind is focused differently upon a life issue via the cards, the door is open for new ways to direct one's energy--or ways to alter one's future. This is the beauty of any divination.
This type of knowledge was seen as sacred, and only for the few. Kings employed astrologers and diviners so as to have this sacred access to Universal patterns. Eventually, the Church sought to eradicate access to all such knowledge by deeming it 'evil'. Today we are fortunate to live in a time when access to knowledge is largely tolerated. We are free to explore the energetic patterns around us and to discover how we fit into the Universal scheme.