It creates a set of symlinks so every program sees exactly the dependencies it needs.
https://nixos.org/guides/nix-pills/09-automatic-runtime-dependencies#automatic-runtime-dependencies
You can also create a container:
https://nixos.wiki/wiki/NixOS_Containers
Or you can create reproducible docker containers with nix:
https://dev.to/anurag_vishwakarma/a-better-way-to-build-reproducible-docker-images-with-nix-2k59
The secret sauce with nix is reproducibility. If it builds once, it will continue building exactly like that forever. Bit by bit.
The fourth can is the one where he packed Kinski’s tongue after he died.