Concept design in games is the theory of designing a game with the story, the art, and the ideas for it to follow to make money from users. The theories are tested and, most likely, updated as a result of playing them. 

As such, the games are research instruments, and people studying design would benefit the most by creating their own games tailored to their own goals, beliefs, and potential customers’ needs. Indeed, while playing such games is a good way to learn about design, building them can teach you far more.