IMHO and my own understanding...
To return to this "mother", how? Being a virtuous person who avoids unvirtuous thinking, speaking, and action, is the basis. However, returning to the Tao is not merely practising good deeds, but also removing all dualisms, grasping, craving of things, concepts of things including the Tao.
Once these (dualisms, grasping, craving, etc) are in place, the mind grasps and creates all sorts of dualism and "strays away" from the Tao. The Yin/Yang aspect of the Tao is not the Tao. We mistake the Yin itself, or Yang itself, as the Tao on its whole. The Yin, or the Yang, cannot exist alone. Seperating them is a big mistake. Thus we need to eliminate all these confusion.
However the "one" in Tao does not mean eliminating all differences. The differences are present in the One in a mysterious way. That's why the Yin and Yang aspect is there. They are not separated anymore, and yet they are there.
Taoism teaches non-duality. It means that light and shade, long and short, black and white, can only be experienced in relation to each other; light is not independent of shade, nor black of white. There are no opposites, only relationships.
What is the Tao? Sorry, I don't know how to describe it. We can try all means of using different words to describe it, but its still not the absolute. The Tao is such, the more one describes, the more likely one is going to grasp on the concept and this is what one will need to avoid in order to be one with Tao.
The tao that can be told
is not the eternal Tao
The name that can be named
is not the eternal Name.
The unnamable is the eternally real.
Naming is the origin
of all particular things.
Free from desire, you realize the mystery.
Caught in desire, you see only the manifestations.
Yet mystery and manifestations
arise from the same source.
This source is called darkness.
Darkness within darkness.
The gateway to all understanding.
- 1st chapter of Tao Te Ching