What is friendly 420?

Excuse me, could you please elaborate on the term 'friendly 420'? I'm not entirely familiar with its meaning or context. Is it a slang term or a specific term used within a particular community? Could you provide some background information on its origins and how it's commonly used? Additionally, I'm curious to know if it has any relevance or connection to the cryptocurrency or finance industry, or if it's purely a social or cultural reference.