This poem is about choices. The road is symbolic of choice. The verbs are in the past tense, so the poet is looking back on the choice he made. The poet was walking in the woods and came to two roads, each leading in a different direction. Which road should he take? He was indecisive about his choice. Both of the roads looked like good ones - both of the choices were appealing to him. He wished he could travel on both roads, or make both choices. He finally made a choice - he chose the road that looked like it had been less traveled. He says that this choice has made all the difference in his life. Many scholars believe the poet is talking about Frost's choice to become a poet, not a very popular or common choice for people, but one which has made "all the difference" in this poet's life.
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There are a couple of other things to consider in this poem. First notice the fact that it is a yellow wood -- this suggests that it is fall. If life is metaphorically a year long, then fall is the late adulthood life, before the winter which represents old age and death. The narrator is commenting on choices he has made in his life once he was an adult. We have no clues as to what the choice was, but he concludes by saying it has made all the difference. That line can be interpreted in both a positive and negative way. The choice could have made all of the difference for the better, or the choice could have made the difference because it led to a life a difficulty. We don't know how the poet intends the line to be interpreted, but that is kind of his last point. All the choices we make in our lives make all the difference to how we live our lives. Big or small, good or bad, all choices affect us.
Understanding a poem is simple if you understand its summary and here is a detailed summary of the poem:-
In the first stanza, the speaker, while walking on an autumn day in a forest where leaves have changed to yellow comes across two roads. He has to choose between the two roads diverging in different directions. He feels sorry that he cannot follow both the roads. So in order to make his decisions about which road to take, he pauses for a long time while and continues looking at one of the roads as far as he can till the road curves into the bushes.
In the second stanza the speaker decides to take the other road as it appears to have been used less than the first. But then he realises that they are actually similarly worn out. The second one that he takes seems to be less travelled by, but as he thinks about it, he realises that they are really about the same.
In the third stanza the speaker continues to think deeply about the possible differences between the two roads. On that particular morning he notices that the leaves that have on fallen on both the roads are still quite yellow and not crushed by human feet. Though the speaker has already opted for the roads less travelled by, he wishes that one day he may come back and walk the first road; but he doubts whether he would be able to do that because in life one thing leads to another and it hardly gives anyone a chance to change tracks.
In the fourth stanza, the speaker considers how the choice he makes now will affect him in future. He says that he would tell with a sigh that two roads diverged in a wood and he choose the one which was less travelled and that made all the difference