What is gVisor? -- explain where runsc is at in the diagram...

I'm trying to dive deeper and understand the project. The diagram above "What is runsc?" shows a set of processes that gVisor starts but it doesn't show runsc. Does this start and then exit? Where would this be in the diagram?

On a related note, I'm curious to understand what the diagram would look like after fork + exec occurs. I'm curious to understand where these calls are made and what happens in this case.

(I'll look at the codebase to try to understand this, but other newbs might have similar confusion.)