Could someone explain the cliffnotes on "vtubers", and the hatsune blue haired person??/mascot??/brand??, and whether they are related?

I see people talking about what as far as I can tell are cartoons performing shows and I'm quite lost. Looking stuff up there's all this jargon that makes it impenetrable. From what I can tell there are like digital puppets that various people perform under? But sometimes the performers "graduate"? (taken behind the shed and shot?) and then sometimes the puppet is gone but then this blue haired thing persists? are they totally different things?

How do you see a performance by a digital puppet? is it all just on screen?

confused boomer noises