These are many public, Internet accessible repositories with most of them focused on popular, open source applications. These repositories do not require authentication for access.
The controller provides out of box support in every project for a few public repositories that are frequently used by developers and operational personnel.
If necessary, users of the project can edit and delete these repositories.
Bitnami maintains a curated, Helm repository with a number of popular open source applications.
Cert-Manager builds on top of Kubernetes, introducing certificate authorities and certificates as first-class resource types in the Kubernetes API. They host a public repository for their artifacts.