This is a great question to think about. Remember, there are many quotes that you could use to answer it, but if I were you, I would turn to the final stanza, and use that to point out the symbolic meaning of this poem and how it operates on both a literal and a more metaphorical level:
I shall be telling this with a sigh
Somwhere ages and ages hence:
Two roads diverged in a wood, and I--
I took the one less travelled by,
And that has made all the difference.
Clearly we can see how this poem works on a literal level. A man is walking through the woods and comes to a fork and needs to pick one. Both appear to be similar and so he has to make a random choice. However, this choice becomes symbolically important for him. The final line of the poem, "And that has made all the difference," suggests that there is something much deeper going on than having to choose between two identical paths, and points towards the way that in our lives we have to make big decisions without knowing what the outcomes of those decisions are, and are often left haunted by the outcomes of those decisions. The way that the speaker remembers this "ages and ages hence" indicates just how important this life decision was, and the "sigh" with which he tells his tale shows how he is still preoccupied with his decision and how he imagines what his life would have been like if he had taken the other path.