Game prototyping is one of the most important parts of the game development process.
It consists of creating a method to test the game concept. It is a way to test if the video game is viable in practice without investing too much money and time.
Prototyping is also used to find methods to optimize the game mechanics and make it as fun as possible.
It does not matter if the prototype development is done on paper or created in a digital environment. Generally, a rough and fast game prototype is used for quality testing and learning in the early stages.
More detailed prototypes are useful for testing or pilot testing near the end of the project.