Looked at but not seen, it is called invisible.
Listened to but not heard, it is called soundless.
Grasped for but not held, it is called formless.
These three attributes cannot be analyzed,
since they are inseparable.
The top of the Way is not bright
the underside is not dark.
Drawn out forever, nameless,
Forever returning to nonexistence.
Without form or substance,
it is an indistinct shadow.
Stand before it, and you won't see its face.
Follow it, and you won't see its back.
But hold fast to the ancient Way, and you can understand the present.
Know the ancient beginning; this ties together the teachings of the Way.
This is the first metaphysical passage other than Verse 1, which is easier to translate both because the original Chinese is easier, and because it's been analyzed practically to death by other translators. Verse 14 is more challenging. It's clearly meant to be describing the Way, but what kind of attributes is it assigning to it? I think the descriptions here are remarkably consistent, and may all have been written by the same author at the same time. The Way is invisible, soundless, and formless; it can't be analyzed. This fits exactly with the claim of Verse 1 that the Way that be described is not the true Way. The second section reiterates this description, avowing that the Way cannot be described by recourse to physical metaphors like light and dark. There is some beautiful imagery here; The phrase I've translated as "Drawn out forever" is [sheng sheng], a repeated character which can mean continuous, neverending, and infinite, and which evokes a thread because it uses the thread radical.
The first part of the third section is more of the same: the Way cannot be described as having a front and back, at least not as we understand them. But what to make of the last two sentences? What is this talk about "ancient Way?" There are two things necessary to understand this. First, remember that the Way is said to be very old, in one verse it is even said that it predates the gods. Another important element to the meaning is that Chinese philosophers around the time of the Tao Te Ching used "ancient" as a way of referring to ideas or principles they liked. In later verses we'll see statements like "Ancient kings did X, and everything was wonderful." It's important to understand that the authors of the TTC didn't really base their recommendations on archeological evidence of what ancient kings or people did, they're just using "ancient" as a signal to tell you they agree with something. Of course, it's not completely just a rhetorical device, because records of ancient times were sparse and most people probably did believe, to some degree, that things really were better in the "good old days." Suffice it to say that according to other, opposing philosophical and moral traditions, ancient kings were said to be behaving very differently!