Hi everyone

Can someone provide me with more information about this topic?

I did not understand this part of the book very well.

Rian Stone tries to explain a little in his video:

https://www.youtube.com/watch?v=frfzN4T0VrA&list=PLXmCJkDEG4IopqTVgVDr78wUWNRwdJMSD&index=5

But I don't fully understand the concept yet.