Questions about Vtubers and Vtubing

Hello, I just wanted to ask a few questions about Vtubing and Vtubers because I really don't know much about it and I figured people here would best know the answers to my questions.

- Can someone provide a small summary of what Vtubing is?

From my understanding, there are multiple companies (English and Japanese?) that run all of these Vtubers and (Manage?) them. Also, there are multiple (Generations?) or sections of Vtubers that are (different?) From one another. I know that hololive is one of these companies, and I think its the (biggest?)
Anything else anyone can tell me is much appreciated, thanks!