Laozi at 90 years old he was tired of government work and decided to leave China. Someone asked him to write a book called Dao De Jing. the Dao De Jing it preached a return to a simple and natural way of living.
True harmony comes from balancing the opposite forces of nature, called yin and yang.Yin means "shaded," and yang means "sunlit." To Daoists, nature is full of opposites, like life and death, or light and darkness.
This symbol is called Eight Trigrams it is also know as the Bagua. It represents the fundamental principles of reality.
The Dao De Jing is apart of Daoism because a guard was sad that Laozi was leaving from government and he was afraid the great teachers wisdom would be lost from China. The Dao De Jing preached a return to a simple and natural way of living life.