What's the difference between GFI and GFCI?

As a cryptocurrency enthusiast and finance practitioner, I'm often intrigued by the nuances of various financial instruments and protocols. Could you elaborate on the key distinctions between GFI and GFCI? Are they both related to financial indices or do they serve distinct purposes? Understanding their core functionalities and potential applications in the crypto ecosystem would greatly aid in my comprehension of this rapidly evolving domain. Clarifying their differences would provide valuable insights for investors and enthusiasts alike.