A distribution file is the packaged release artifact that an installation tool downloads from a software registry. In Python ecosystems, this may be a wheel or source archive that contains the code and metadata needed to install a specific version of a package.
Distribution files matter because they are the concrete objects users and build systems trust. If an attacker can replace or add a file to an existing release, they may be able to poison a package without creating a new project. Defenders therefore treat upload controls, signing, and registry policy as part of supply-chain security. Limiting when distribution files can be added or changed helps reduce the value of stolen credentials, compromised publishing tokens, and abused automation workflows.