What do "exhibitor" and "vendor" mean here?

We use vendor for any business or organization that sets up at events — crafters, food trucks, home-improvement companies, breweries, nonprofits, government outreach booths, all of it. An exhibitor is a vendor at a specific event: "the exhibitor list for the Topsfield Fair" means the vendors who were there that year.

Your single vendor listing carries your whole event history. Each event page shows its own exhibitor roster for that occurrence, so a fairgoer can see who'll be at this year's show — and who was at last year's.