Tao 道 the origin, the universe, the laws, everything - Tao is.

Tao 道

The ancient text of Taoism, the ever mystical Tao De Jing 道德經 has this excerpt to describe Tao: 

道可道，非常道；

The Way that can be told of is not an unvarying way;

名可名，非常名。

The names that can be named are not unvarying names,

无名，天地之始；

It was from the Nameless that Heaven and Earth sprang;

有名，万物之母。

The named is but the mother that rears the ten thousand creatures, each after its kind.

The text does not seem to help much in explaining what Tao is, interpretation could be subjective. 

TaiJi diagram, a presentation of Yin and Yang

In my understanding, what the text means is that the name Tao does not represent the true Tao, as it is nameless, it is called Tao just as a reference, for the part of Tao that we know. The true Tao is unknown, and from the unknown Heaven and Earth came, from the Tao we know, we know all things known to us.

On the subject of origin, the text says:

道生一、一生二、二生三、三生萬物

Tao begets one, one begets two, two begets three and three begets ten thousands beings.

Another perplexing text. 

The Chinese Trinity, The Grand Pure, The Supreme Pure ,The Jade Pure.

Tao begets One, 

Why One? and what is One? Could One be God? The universe? or existence? No one can be certain, but we know from the text we can be sure that Tao is not the One.

One begets Two, 

On this, most people would agree that Two denotes Yin and Yang. 

The Hindu Trinity: Brama, Vishnu and Shiva

Two begets Three, 

What is Three? According to religious Taoism, Three represents the Chinese Trinity, the Three Pure Ones 三清, highest pantheons in Chinese folk religion. Could be the Hindu trinity or the Christian trinity too, subject to each's belief. 

And Three begets Ten thousand beings, that is all the things that we know.

So here comes the question again, What is Tao? IMO, Tao is possibly all the things we know and we don't, I've been told Tao is the way the universe breathes, is unknown, is the origin, is inside us and outside us, is everything that we know and that we don't, is the beginning, the journey and the end. To me these descriptions of what Tao is are correct, or at least partially correct, because Tao is.