Docker Hub is the world's largest public registry for hosting Docker images. It is the default download source when you are working with docker.
A Docker image is a file with a set of instructions for building a Docker container. It is like a snapshot in virtual machine (VM) environments.
Docker creates, runs and deploys applications in containers. When a user runs an image, it can become one or many instances of a container.
PMCs can host convenience binaries on Docker Hub for users to download and deploy. The ASF has a limited number of Docker Hub seats, so there is a limit of YYYY seats per PMC.