I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I— I took the one less traveled by, And that has made all the difference.
I believe that Robert Frost is referring to how one's choices in life form the pattern for what follows. Not only what we choose, but what we do not choose. In an earlier stanza, he also refers to the possibility of returning and taking the other road, the one more traveled, simply so that he can experience it to know what he may have missed. Although we can never know what exactly he experienced on that "road less traveled by", we can assume that it had a huge impact on his life, one which he will be talking about "ages and ages hence". I adore Robert Frost's poetry!
The poet of Road Not Taken will be telling how at the time of decision, the choices one has seems feasible and ripe for success. He wants to convey that journeys you take in life will change the person you are. They will never be smooth sailing, therefore you need to make decisions carefully.
Simply stated, he's telling future generations to make their own decisions and not blindly follow the crowd. The fork in the road represents choices we make in life. By taking the road less traveled Frost demonstrates the ability to make his own informed decisions. And, as the poem ends, "That has made all the difference."
When you ask a question like this indicate who and what you are talking about since not everyone is familiar with Robert Frost.
I like FatKennys answer above the most. That the narrator of the poem did his own thing in life, even if it turned out to be harder and rougher, rather than follow the easier road along with everyone else.