Nix really is a purely functional, lazily evaluated language that is great at expressing dependencies in your project. You can think of it as a make on steroids

Nix really is a purely functional, lazily evaluated language that is great at expressing dependencies in your project. You can think of it as a make on steroids, but it is much more than that. Because the language expresses what to build from a known state (i.e. nothing is installed) together with its purely functional properties, means that for the same input (source code, dependencies, configuration options, system architecture etc) it supposed to always generate the same output. Nix can be think of as package manager, and its nix-env command (which BTW is discouraged from Nix purist to use[1]) behaves like a package manager, but IMO it's more of a build system. After the author of Nix wrote his thesis he mentioned that the language can describe an entire operating system. That's how NixOS happened. You can have a single configuration file that describes what needs to be installed on your OS how configured etc. The great thing is that you can take such configuration file, and recreate another machine with it configured exactly as you want it. No need for chef/salt/ansible etc. It actually has an edge over these tools, for example if you tell that specific package needs to to be installed, and than later you remove the package from the config, nix will remove that package as well (with chef/salt/ansible, you would need to add a state that's uninstalling the package), another benefit is that all changes are atomic, you either have your changes applied or nothing is changed, there's nothing in between (this makes things like replacing X11 with Wayland, or KDE with Gnome just another change, that you can always revert). It's a very powerful tool, and the more I use the more amazing it seems. It shows that if you target specific problems the right way a lot of common headaches are eliminated. [1] it's advisable to never install packages by hand using nix-env, since that adds mutability to your system, instead you should use nix-shell (another great tool) to temporarily make specific application available, use the global configuration.nix to install packages globally on the system, or use home-manager extension which allows you to configure each home directory (that means what dot files do, but also each user can have their individual packages, and goes further, for example you can even control what extensions firefox should have installed)