Software Supply Chain
Package Registry
Also: registry, package index
A public or private service that stores published packages and hands them out by name and version, such as npm or PyPI.
In more detail
When you run an install command, your package manager asks a registry for a name and a version and trusts the answer. Registries mostly check who is allowed to publish under a name, not whether the code is safe, which is why takeover of a publishing account is such an effective attack.