Where can I find documentation on the built-in tools or how certain settings work?
On the tools
Documentation on the built-in tools and how to use them can easily be found on the editor's documentation or via the man pages provided with the default packages. For this purpose, centralized manpages have been created and managed by us.
About the functioning of a Debian or apt distribution for example
There is no lack of documentation from Debian or others on the internet, and it can be a comprehensive source of documentation. Overall, the man pages will suffice in most cases. In case this is not enough, even though we try to provide as much documentation as possible, the internet is still your best bet.