It is nature. It is existence and non-existence that we are living in. The Chinese conception of the universe is derived from the philosophy of the Dao. It is the infinite that humans cannot understand because it is the infinite. It involves everything from the extremely small to the extremely large. It is the gases, stars, and planets of the universe, and the emptiness that is expanding which pushes the galaxies away from each other. It includes the quarks that make up the protons, electrons and neutrons which make up atoms that make up everything in the universe. The philosophy of the Dao is extensive and has been understood in many ways. It is even the thoughts we create and the collective consciousness, so understanding it is important in how we live.
Many people translate it as "the way". Since the Dao is intricate, in English it is not easy to translate. This translation is talking about that we need to 'follow the way of what is naturally so'. It is a pathway to find strength, harmony, peace and health.
The Chinese philosophy has a unique view of the infinite.
The Dao is not just a philosophy, it is a way of following nature.
Science is studying life, and Dao is life.