Not sure if trolling, or genuinely doesn't know...
The term 'racing cars' covers any car that has been modified, or built, for the purpose of racing - this includes all types of open-wheelers, GT cars, drag racers, rally cars, etc... and, of course, sports cars.
To qualify specifically as a sports car, they have to be built as if there would normally be 2 seats. Of course they only put 1 seat in it, same as any other racing car (except rally cars), but you'll notice that the seat is always set to one side of the car.