In this poem, a traveler comes to a fork in a road and must decide which way he wants to go. He is "sorry [he] could not travel both [roads]." He stares for a long time down one of the roads.
In stanza two, he examines the other road. In stanza three, he picks the second road. We know this because he says: "Oh, I kept the first [road] for another day!" In saying this, he reveals his desire to go down both roads. He rationalizes his choice to himself by saying, in essence, I'll come back and explore that other road another day.
I took the one less traveled by,And that has made all the difference.