Check out https://zero-to-nix.com/concepts/closures https://zero-to-nix.com/concepts/closures and https://zero-to-nix.com/concepts/realisation https://zero-to-n

Check out https://zero-to-nix.com/concepts/closures https://zero-to-nix.com/concepts/closures and https://zero-to-nix.com/concepts/realisation https://zero-to-nix.com/concepts/realisation, which I think add more color to this (and also is largely authored by biggestlou here.)