Gran Turismo Concept (グランツーリスモ コンセプト Guran Tsūrisumo Konseputo) is a racing video game of the Gran Turismo series for PlayStation 2 which is developed by Polyphony Digital. It is essentially a short version of Gran Turismo 3: A-Spec, but with concept cars that ended up in Gran Turismo 4. For undisclosed reasons, the game was not released in the North American market.
The 2001 Tokyo game features Tokyo Motor Show 2001 concept cars including the Nissan GT-R Concept '01.
A second version, 2002 Tokyo-Seoul, was released in Korea to celebrate the PlayStation 2 official launch in that country. It featured cars from the 2001 Tokyo version plus additional models unveiled at the Seoul Motor Show. This game introduced South Korean automakers, like Hyundai, in the Gran Turismo series.
A last version, 2002 Tokyo-Geneva, was released in Europe and featured all the cars from the 2002 Tokyo-Seoul version plus new models unveiled at the Geneva Motor Show including the Volkswagen W12. The 2002 Tokyo-Geneva is the definitive version of GT Concept, as it has the most cars, including the Ford GT40 LM Edition.
Source: Wikipedia, "Gran Turismo Concept", available under the CC-BY-SA License.