Docker Hub is the most widely used public container registry, averaging over one billion image pulls per month at the time of writing. You can host unlimited public repositories on the Hub and pay a subscription to host multiple private repositories.

Docker Hub has an automated build system, so you can link image repositories to source code repositories in GitHub or Bitbucket, and Docker's servers will build an image from the Dockerfile in the repository whenever you push changes – it's a simple and effective hosted Continuous Integration (CI) solution, especially if you are using portable, multi-stage Dockerfiles.

A Hub subscription is suitable for smaller projects or teams with multiple users working on the same applications. It has an authorization framework where users can create an organization, which becomes the account name in the repository rather than an individual user's account name. Many users can be given access to the organization's repositories, which allows multiple users to push images.

Docker Hub is also a registry for commercial software distribution. It's like an app store for server-side applications. If your company produces commercial software, Docker Hub could be a good choice for distributing it. You build and push images in exactly the same way, but your source can be kept private – only the packaged application is publicly available.

You can register with Docker as a Verified Publisher to identify that there's a commercial entity maintaining the images. Docker Hub lets you filter on Verified Publishers, so this is a good way to get visibility for your apps:

There is also a certification process you can go through for images which are hosted on Docker Hub. Docker certification applies across software images and hardware stacks. If your image is certified, it's guaranteed to work on Docker Enterprise on any certified hardware. Docker tests all of these combinations in the certification process, and that end-to-end guarantee is very attractive to large enterprises.