The tone is wistful open-minded, and regretful. The narrator is open-minded enough to decide to take a different road than the one most often used. The narrator regretted not being able to go though both roads.
The word choice shows many elements of adventure and travel. "travel", "traveler", "passing" The poem is about traveling through a different path and trying something different.
"I took the one less traveled by, And it has made all the difference."
The trail that the narrator takes is described with language that shows the readers how abandoned and unused the trail is. "To where it bent in the undergrowth," and "Because it was grassy and wanted wear."
"The Road Not Taken"
The style is very travel and adventure based. "travel", "traveler", "way leads on to way" "Way leads on to way" can mean that an adventure continues on for a long time.
"Yet knowing how way leads on to way, I doubted if I should ever come back."
The theme is that sometimes something less popular and used can be so much better. "I took the one less traveled by, And it has made all the difference." Frost essentially says life is an adventure and taking a different path can change it for the better.