What is the difference between game development and game design?

Game designing is creating look and feel of the game where as game development is the backend coding part. Game designing is more art related on the other hand game development is majorly programming based.

Game designing is a creative activity where you work on your idea and develop game concepts and high level requirements of game. It then lead to technical design of game. Once technical design is over developers develop( write software code) game. Development also include game software testing.

Disign is art part. Whereas development is programmimg part.

they mixed together,u can say game development is the super set of game design where game design is the subset of game development.