Hi,
I am not sure what you really want us to tell you, but from watching your YouTube post, all I can say here is that I see a Teacher trying to explain to you the principle of software evolution and how you would document that evolution of the software for others to pick up, understand and develop upon further in the future.
This is an expected process in any corporate / business scenario to ensure that no one person becomes a "font of knowledge" that no one else can then pick up and take forward for future and further development.
Hope that helps.
Cheers,
Ian
