Docker Hub is the original Docker registry, provided by Docker themselves. This registry stores a vast number of Docker images, some of which come from Docker and some of which have been built for them by software teams.
In this chapter, we aren't going to cover installing Docker, as installing it and setting it up is a chapter in its own right, especially since installing Docker on Windows is a different experience to installing Docker on macOS or Linux. The commands that we will use to compose Docker applications and check the state of instances don't change though, so we will cover them as and when they are needed.