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Wiktionary
concept car

n. (context automotive English) An automobile which is not available for retail sale and which is usually only a mock-up having limited functionality, but which may be displayed at auto shows to represent design ideas under consideration for future vehicles.

Wikipedia
Concept car

A concept car (also known as concept vehicle, show vehicle or prototype) is a car made to showcase new styling and/or new technology. They are often shown at motor shows to gauge customer reaction to new and radical designs which may or may not be mass-produced. General Motors designer Harley Earl is generally credited with inventing the concept car, and did much to popularize it through its traveling Motorama shows of the 1950s.

Concept cars never go into production directly. In modern times all would have to undergo many changes before the design is finalized for the sake of practicality, safety, regulatory compliance, and cost. A " production-intent" vehicle, as opposed to a concept vehicle, serves this purpose. They are also known as prototype cars, but should not be confused with prototype race cars such as the Le Mans Prototype.