This article is a good explanation of how nix works at a high level, and I'm excited to see nix getting some really prominent support, but for some reason it never tells you what the point of all of this is, so I think many folks might feel turned off by it. In other words, I don't believe it ever compellingly answers the question that constitutes its title. The word "package" doesn't even appear until near the end of the article! This is probably a second or third article to read about nix rather than the very first thing that exposes you to it.

The point of nix is just to create completely reproducible builds and package management, including support for multiple versions of packages side-by-size with no issues. It's sort of a next-generation package management system that tries to avoid most of the pitfalls that OS package managers have fumbled with up to this point. It's really that simple.

"nix" as a term refers to a system of multiple components that work together to achieve that goal. There's the package manager itself (called Nix), the language that build instructions are written in (also called Nix), an existing ecosystem of predefined packages (called nixpkgs), and an optional Linux distro that uses Nix the package manager as its package manager (called NixOS).