What is a shhhh?

Excuse me, could you possibly elaborate on what exactly a 'shhhh' is? I've heard the term mentioned in a few conversations lately, but I'm struggling to grasp its exact meaning. Is it some form of slang or a specialized term within the realm of cryptocurrency or finance? If so, how is it relevant and how is it used in practical applications? I'd be very grateful for any clarification you could provide.