Docker utilizes a hierarchical system for storing images, as shown in the following diagram:
The first component in this system is the registry. The images you build will be stored in a remote registry for others to use. Docker registry is a service (an application, in fact) that stores your Docker images. Docker Hub is an example of the publicly available registry - it's free and serves a huge, constantly growing collection of existing images. We are going to cover Docker Hub in detail in Chapter 5, Finding Images. There are, of course, other registries available on the Internet, such as Artifactory (https://www.jfrog.com/artifactory), Google Container Registry (https://cloud.google.com/container-registry), and Quay (https://quay.io).
The repository, on the other hand, is a collection (namespace) of related images, usually providing different versions of the same application or service. In other words, it is a collection of different docker images with...