In Lao Tzu's own words, the Tao is:
The tao that can be told
is not the eternal Tao.
The Tao is like an empty container:
it can never be emptied and can never be filled.
Infinitely deep, it is the source of all things.
The Tao of Heaven is eternal,
and the earth is long enduring.
Why are they long enduring?
They do not live for themselves;
thus they are present for all beings.
The supreme good is like water,
which benefits all of creation
without trying to compete with it.
It gathers in unpopular places.
Thus it is like the Tao.
Look for it, and it can't be seen.
Listen for it, and it can't be heard.
Grasp for it, and it can't be caught.
These three cannot be further described,
so we treat them as The One.
the Tao is constant
The greatest virtue you can have
comes from following only the Tao;
which takes a form that is intangible and evasive.
Since the beginning of time, the Tao has always existed.
It is beyond existing and not existing .
Humanity follows the earth.
Earth follows Heaven.
Heaven follows the Tao.
The Tao follows only itself.
The Tao is nameless and unchanging.
Although it appears insignificant,
nothing in the world can contain it.
All things end in the Tao
just as the small streams and the largest rivers
flow through valleys to the sea.