There is no exact definition of a sports car, but it is typically a two-seater two-door automobile designed for performance - speed, maneuverability, acceleration. Often open, or convertible, but not necessarily. Some sports cars may have small emergency back seats that are really only suitable for luggage. A sports car never has four doors or a full back seat.
Well known specialist brands or marques, new and old, are: AC, Alfa Romeo, Alpine, Aston Martin, Austin-Healey, Bricklin, Bugatti, Caterham, De Lorean, Donkervoort, Ferrari, HKT, Jaguar, Lamborghini, Lotus, McLaren, Maserati, MG, Morgan, Porsche Triumph, TVR. Almost all major car manufacturers also make some form of high performance car, sometimes very successfully such as Ford with the GT40.