"I Ching", also known as the "Classic of Changes" or "Book of Changes" in English, is an ancient divination text and the oldest of the Chinese classics. The I Ching was originally a divination manual in the Western Zhou period, but over the course of the Warring States period and early imperial period was transformed into a Religious cosmology/cosmological text with a series of philosophical commentaries known as the "Ten Wings." After becoming part of the Five Classics in the 2nd century BC, the I Ching was the subject of scholarly commentary and the basis for divination practice for centuries across the Far East, and eventually took on an influential role in Western understanding of Eastern thought.
The I Ching uses a type of divination called cleromancy, which produces apparently random numbers. Six random numbers are turned into a hexagram, which can then be looked up in the I Ching book, arranged in an order known as the King Wen sequence. The interpretation of the readings found in the I Ching is the matter of centuries of debate, and many commentators have used the book symbolically, often to provide guidance for moral decision-making as informed by Confucianism. The hexagrams themselves have often acquired cosmological significance and paralleled with many other traditional names for the processes of change such as yin and yang and Wu Xing.More I Ching on Wikipedia.