Nix as a package manager is a subset of a broader concept of a graph database of reproducible build instructions that explicitly track every dependency of your

Nix as a package manager is a subset of a broader concept of a graph database of reproducible build instructions that explicitly track every dependency of your project, and a set of tools that allow you to build and cache said dependencies in an isolated, distributed (parallel), and transparent way. Add filesystem- / path-sandboxing to the equation and you'll get a set of features that make Nix different to other conventional package managers.