What does it mean to be bygone?

Excuse me, but I'm curious to understand something. Could you please elaborate on the phrase "what does it mean to be bygone?"? It seems to carry a sense of something that's passed away or no longer exists, but I'd like to hear your interpretation of its precise meaning, especially in a broader context. Is it simply referring to the past, or does it encompass a deeper sense of loss or irretrievability? I'm interested in your thoughts on how this phrase might relate to various aspects of life, such as memories, relationships, or even trends in the world of finance and cryptocurrency.