A traditional coupe usually trades separate rear passenger doors for a two-door body and a lower, more closely shaped roofline. A luxury sedan typically combines four-door access with an emphasis on comfort, refinement, and premium equipment. The clearest differences are how people enter, where they sit, and which compromises the body makes for its shape.
Luxury is not exclusive to sedans, and sporty driving is not exclusive to coupes. A coupe can be luxurious, while a sedan can be performance-focused. Compare the actual passenger access, seating, luggage space, ride, and equipment before treating either description as a promise about the whole car.