What is a game prototype? Certainly, there is a short and elegant definition. But I like how Jesse Schell explains it in his famous book The Art of Game Design. He says that the sole purpose of a game prototype is to answer a question or questions that arise during game development. Questions could be general like: “Is this game mechanic fun?” or very specific: “Does my team have enough experience to produce animations of given quality?”
When I just started my experiments in game development I did not know about prototyping. I had just a blurry vision of how a game development process should look like.