Since they are interrelated, one must bear in mind the fact that the Dao is something like an omni-principle underlying all things, whereas De exhibits the power of the Dao through observable functions.
[3] Such characteristics of the Dao as those of being "vague and elusive" correspond to its indescribability and intangibility, and therein lies the wellspring of the "coming-into-being" of all things.
[4] In the Inner Chapters of the Guang Zi (Guang Zi Nei Pian ) jing is interpreted as qi, and regarded as the origin of energy. It is rendered here in English as "the essence," according to Yan Ling-feng and Chan Wing-tsit, who annotates that "The word ching (the Chinese pronunciation of which is jing) also means intelligence, spirit or life force. "The essence" may be supposed to imply "the essential qi as the origin of vital energy or the life force."
[5] "The proof" refers to the fact that "the essence" as the vital qi or energy is working constantly, even though it is invisible.
[6] A number of the Dao De Jing versions (e.g. those of Heshang Gong and Wang Bi) present the expression zi jin ji gu (from the present back to the past) the other way round as zi gu ji jin (from the past till the present). My correction follows the Mawangdui version of the Dao De Jing. In addition, another reason is that the Chinese word gu rhymes with fu at the end of the subsequent expression yi yue zhong fu (we may know the beginning of all things).
[7] The word fu can be literally identified with the word for father in the ancient Chinese language. It is actually used here to denote shi (beginning). "The beginning of all things" is equivalent to "the origin of the universe."
[8] Here "this" stands for the Dao or "the nature of the Dao."

Commentary:
Depicted in this chapter are the basic characteristics of the Dao, which is incorporeal and invisible, but exists and functions in reality. Hence it is out of the Dao's state of being "vague and elusive" that the myriad things are created and produced. Simply put, the Dao is the originator of the universe and the myriad things in it. This interpretation allows us an overview of how things come into being. During this process "the real" (as things) may be traced back to "the image." And "the image" may be traced back to "the essence"--and "the essence" can then be traced back to the Dao as a state of being "vague and elusive."
In addition, this chapter exposes the character of De as the manifestation of the Dao. The former represents in a tangible mode the latter as an omni-principle or omni-determinant underlying all things. The concept of De is manifold: It can be the attributes of things in the physical world; it can be the functions of affairs in the human society; and, above all, it can be the virtue of a person in the course of the cultivation of his or her personality. The interrelationship between the Dao and De is interdependent to the extent that the former, as the source of creation, is shown or made known through the latter. It is unlike the relationship between the Platonic "Idea" (eidos) of a bed and "the bed" itself, for the simple reason that the former is absolute while the latter is the mimesis or shadow of the former. There is obviously a kind of ranking involved here in the sense of different values.
It should be pointed out that the historical development of Chinese artistic theory finds a permanent and permeable influence originating in the following statements: "Elusive and vague as it is, there is the image in it. Vague and elusive as it is, there is the real in it. Profound and obscure as it is, there is the essence in it." The Dao of Chinese art is said to lie in the ideal and achievement of yi jing (the highest reach of the artistic spirit), which is largely determined by xiang wai zhi xiang (image beyond form) and yun wai zhi zhi (significance beyond charm), among other characteristics. Take Chinese landscape painting (freehand brushwork painting in particular) for example: It always places the stress on the realization of vi jing and shen si (spirit-alikeness). Thus the Chinese artist tends to care far less than his occidental counterpart for perspective as a technique to produce three-dimensionality and life likeness as a result of elaborate imitation; rather, he pays much more attention to creating a vivid touch to convey the spirit, meanwhile using form to show the spirit as well. That is why Chinese freehand brushwork painting is often characterized by spontaneous expression and bold outline instead of an authentically identifiable form or object. It would be relevant and instructive to make a reference to the following reference in Chapter 14: "It is called shape without shape or image without object. It is also called a state of being vague and elusive."
2.4 (Chapter 5)
Heaven and Earth are not humane.[1]
They regard all things as straw dogs.[2]

(1)(2)(3)(4)(5)