Who is Lao-tzu from Tao Te Ching and what is their importance?

The author of the TAO TE CHING, Lao-tzu is perhaps Confucius' older contemporary (551-479 BCE) and may have been an archivist in the petty kingdom of Chou. He has left few traces in history beyond this book, which, Mitchell declares is written out of "grandmotherly kindness" for complicated minds that cannot see simplicity. According to the oldest biography, Lao-tzu lives a long time in the country of Chou but departs when it declines. At the frontier, a guard asks him to write a book teaching him the art of living. Lao-tzu writes it and departs.