What Does Website Isolation / User Isolation Do Laravel Forge?

In Laravel Forge there's an option called Website Isolation, which some people also seem to mention as user isolation as well. I am not quite sure what it does and possible benefit for such functionality. It would be great if someone can explain this!

I found out that one of the biggest advantages for using Website / User Isolation is that Laravel Forge will be then able to offer unique and independent nginx environment compared to other sites exist in the same server. Thus, in situations where it requires restarting an nginx or overloading, other sites in the server should work perfectly fine.