What is a fungible token?

Could you please elaborate on the concept of a fungible token? I've heard the term used frequently in the crypto and blockchain community, but I'm still a bit unclear on its precise definition. As a professional practitioner in the field of cryptocurrency and finance, I'm curious to understand how fungible tokens work and how they differ from other types of digital assets. Could you explain the key characteristics that define a fungible token and provide some examples of how they are being utilized in the current market? Thank you for your assistance in clarifying this important concept.