One of the great aspects about Robert Frost's poetry is the way that symbolism is used to invite multiple meanings, and this is certainly the case here, with various critics arguing this poem is actually about death, the nature of beauty, responsibility and duty and nature. All such meanings can be supported from an analysis of the poem. I have included a link below to the themes section of eNotes based on this poem for you to gain information on these various meanings.
However, one meaning that strikes me as being worthy of discussion is the way that this poem presents nature. An opposition is created in this poem between nature and the modern world that is built up through images of natural objects that are compared with objects we associate with civilisation. Note the way that the woods and the village are compared in the first stanza, just as in the second stanza a farmhouse is compared with a lake. Even the harness bells of the horse act as a representation of man-made society. This contrast seems to suggest that it is actually very difficult for man to retain any meaningful contact with nature in the modern world. As much as the speaker is entranced by the beauty of nature and the sight that he sees, throughout the poem it is clear that he is always reminded of the human world, and finally, in the final stanza, he says that such a moment cannot last and he must return to his world:
The woods are lovely, dark, and deep,
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.
There is a sense in which the obligations of the society of man make any meaningful and lasting relationship with nature impossible, as the speaker sees that his various "promises" and the journeying he has to make are more important than enjoying the sublime beauty of what is before him.