I was under the impression that visitors comprise workers and shoppers from neighbouring cities but tourists spawn out of thin air because in my tourist city, I have ~30000 tourists but barely 300 visitors.
But when I started a new city in an isolated area with no neighbours by road, I had no shoppers or workers from neighbouring cities (because there are none). About ~1800 tourists came through my train station, at the same time, I also had about ~1800 visitors.
So the second scenario contradicts my previous belief. Has anyone figured this out?