From the linked “how to enable flakes” article:

> As you can see, it uses our ./configuration.nix as a module. What are modules again? Per NixOS wiki:

> > Modules are files combined by NixOS to produce the full system configuration. A module contains a Nix expression. It declares options for other modules to define (give a value). It processes them and defines options declared in other modules.

> Simple as.

If only.

Also, the article is very much a How not a Why.