I've noticed on this website, that many coupes are actually listed as "two-door sedans" and I'm wondering just what the difference is? I've performed Google searches on this, but can't find results telling of a difference between the two terms at all. I see in the comments under many cars on this website that many of these cars are "not coupes, but two-door sedans". Is it the car's seating arrangement, windows, or what?

I'm confused...