What's the difference between GFCI and GFI?

Could you elaborate on the key distinctions between GFCI and GFI in the context of electrical safety? I've heard both terms used in relation to grounding and fault protection, but I'm not entirely clear on the specific differences. For instance, is GFCI a more modern standard compared to GFI? Do they have different operational principles? Additionally, which one is more commonly recommended for use in residential or commercial applications? I'd appreciate a concise yet comprehensive explanation to help me understand the nuances between these two technologies.