Symbolism, Imagery, Allegory
You know that whole life-is-a-journey notion? Well, the journey Phoenix takes along the path in the story is kind of like a microcosm (SAT word in the house) of a person's whole life.
Just like in life, you see, the path has easy parts and hard parts. It has parts that are familiar and parts that are surprising. There's beauty, danger, confusion, and wonder. There are times to rest, times to contemplate, and times to push on. You get the gist.
Let's just add one more thing to the significance of the path, though. The particular path Phoenix is on runs like a vein through Mississippi and has seen and participated in much of Mississippi history (more detail on this in the "Setting" section, so check it out). And so, of course, has Phoenix. Boom.