What is a Numista Coin Index?

Could you please explain what exactly is a Numista Coin Index? I'm quite intrigued by the concept and would love to know more about it. Is it a tool used to track the performance of various coins in the market? Or does it have a different purpose entirely? I'm particularly interested in understanding how it works and what benefits it might offer to investors and collectors alike. Any insights you could provide would be greatly appreciated.