A registry is a service that stores, manages, and distributes images. Public services, such as Docker Hub (https://hub.docker.com) and Quay (https://quay.io), collect all kinds of pre-built images of popular tools, such as Ubuntu, nginx, and custom images from other developers. The Alpine Linux tool we've used many times already is actually pulled from Docker Hub (https://hub.docker.com/_/alpine). You can upload your own tool onto these services and share them with everyone else as well.
If you need a private registry, but for some reason you don't want to subscribe to the paid plans of registry service providers, you can always set up one on your own with the Docker Registry (https://hub.docker.com/_/registry). Other ...
