We see the story through the eyes of Sal Paradise, the character who is supposed to mirror Jack Kerouac himself. What’s interesting is the other main character, Dean Moriarty. Sal is, to a degree, slightly obsessed with Dean and focuses on this quite a bit. Sal remains our main character, though. We see his thoughts, not Dean’s, get his background, see him live and talk without Dean there.
Sal’s perspective let’s us hear On the Road as if it’s just another story being told by some truck driver to the hitchhiker he picked up (yes, in this analogy, you are the hitchhiker). Which is cool. It’s colored with some looking-back perspective because of the first person narration, and so we get a bit of insight into the characters that we might otherwise miss.