The whole thought of Laozi is developed around the central concept of Dao. However, the 73 characters of Dao in Laozi have different meanings although the symbol form is unified. In some places, Dao refers to the origin of the existence of the world, in some places, Tao refers to a law, and in some places, Dao refers to a standard of life, which reflects the unified outlook on life of Dao.
The combination of laws of things and principles of life is the Dao in Lao Tzu's saying 'Dao is a process in which everything grows from little to more, from simple to complex'.