What is a FIO handle?

Could you please elaborate on what a FIO handle refers to in the context of cryptocurrency and finance? As a professional in this field, I'm curious to understand its significance and potential applications. Is it a unique identifier for individuals or entities involved in transactions? Does it offer any additional security or privacy benefits? I'm particularly interested in how it differs from other types of identifiers and handles used in this industry. Thank you for clarifying this term for me.