KurtLudwig said:
a book by professor Katie Mack "The End of Everything (Astrophysically Speaking)
This is a pop science book. You would be better served by reading actual textbooks or peer-reviewed papers.
KurtLudwig said:
I did look up on Wikipedia
Did you come across this page:
https://en.wikipedia.org/wiki/False_vacuum_decay
Try reading some of the many scientific papers referenced on that page. That should help to clarify what is being discussed.
KurtLudwig said:
Is False Vacuum a chamber evacuated with almost no molecules of gases?
No.
KurtLudwig said:
Is it a concept in quantum physics?
Yes. It occurs in two main contexts: first, inflation theory (in which the universe during inflation is in a false vacuum state), and second, speculative hypotheses about what might happen to our present universe in the future (involving the speculation that our current universe is in a "false vacuum" state).
The basic underlying idea is that, in quantum field theory, the term "vacuum" doesn't mean "nothing is present at all". It means the lowest energy state possible taking into account all quantum fields that are present and their current states. We usually assume that there is only one such state, but that is not actually true; it is possible in quantum field theory for certain state transitions (for example, the transition at the end of inflation in inflation models) to
change what states are accessible and therefore which state is now the lowest energy state possible, the "vacuum" state.
More detail than that requires having a better reference as a basis for discussion.
KurtLudwig said:
Why is an there energy level difference between a false and true vacuum? How do physicists know how the field value changes? I read somewhere that space is never totally empty do to quantum fluctuations. Why would the laws of the Universe change if it did happen?
All of these questions really should be answered by looking at a specific example. I would recommend reading papers about inflation theory first.