Registries are evolving as generic artifact stores. To enable this goal, the ORAS project provides a way to push and pull OCI Artifacts to and from OCI Registries.
Users seeking a generic registry client can benefit from the ORAS CLI, while developers can build their own clients on top of one of the ORAS client libraries.
The Open Container Initiative (OCI) defines the specifications and standards for container technologies. This includes the API for working with container registries, known formally as the OCI Distribution Specification. (a.k.a. the "distribution-spec").
The distribution-spec was written based on an open-source registry server originally released by the company Docker, which lives on GitHub at distribution/distribution (now a CNCF project).
There are now a number of other open-source and commercial distribution-spec implementations, a list of which can be found here. Registries that implement the distribution-spec are referred to herein as OCI Registries.