Our speaker is out in the woods without a map, and he doesn't know which path to take. But instead of turning tail and running back to where he came from, he chooses a path and forges on, willing to face whatever challenges that path may lead him to. He is attracted to a path that might be less traveled, which suggests that he likes to go where few people have gone before. "The Road Not Taken" embraces exploration, suggesting that the only way to see what's beyond the bend in the road is to keep walking.
Even if both roads seem worn about the same, the speaker tries to take the one less traveled.
The speaker chooses to take the path that he does because it's different from what he originally planned on doing.