Reproducible builds - also known as deterministic builds - are the holy grail of a lot of organizations that care about the authenticity and security of their products. In simple terms it's the ability to produce the exactly same binary build using the same code version and parameters, regardless of where and when it is built, down to a single bit.
This is a companion discussion topic for the original entry at https://our.status.im/reproducable-builds-with-nix/