Here’s a short list of Docker glossary terms worth knowing.
As Docker containers have became widespread, so has a unique set of terms related to creating, deploying and administering containers. If you work with Docker, these are terms you need to know.
They are also, however, terms that can be confusing for the uninitiated. Many of the words and phrases associated with Docker don’t mean what you might think they mean when you first hear them. Container orchestration has nothing to do with musical instruments, for example.
A Short Glossary of Docker Terms
Docker provides a long glossary of container-related terms. You may not need to know all of the words, but you should know the meanings of the following key Docker terms:
Compose is a tool from Docker for creating containerized applications. You use it to write configurations that determine how your containers will run. It’s more or less a form of infrastructure as code, if you count Docker containers as a type of infrastructure.
Docker is both the project that develops Docker containers and, in a more specifically technical sense, it’s the daemon that hosts Docker containers.
Docker Hub is Docker’s official registry service, which runs in the cloud. It’s easy to use, but it’s only one of numerous registry services.
Kubernetes is an open source container orchestrator. Kubernetes has become so popular that its name is now synonymous with container orchestration in some contexts, but Kubernetes is not the only orchestrator out there.
A container orchestrator is a management tool for containers. It helps you deploy and manage containers in production. Kubernetes is the most popular container orchestrator today, but as noted above, there are other choices, such as Docker Swarm.
An image serves as the blueprint for creating containers that will host a certain application or service. Images are designed to be immutable; when you want to update what is inside your containers, you build a new image, rather than update your existing images.
When you pull a container, you download its image from a container registry. Pull in the context of Docker has a similar, though not identical, meaning to Git pulls.
A registry is a place where you store container images. It’s like a GitHub repository, except for containers. Registries can be hosted in the cloud or on-premises.
Somewhat confusingly, Docker uses the term repository to refer to a set of container images that have not yet been deployed to a registry. So, in Docker-speak, a repository is a group of container images that are not yet available for download, which is kind of the opposite of what repository means in most other contexts.
Swarm is Docker’s official container orchestrator. Docker also uses the term swarm to refer to a cluster of containers that are being managed by Swarm (in other words, that are being managed by Docker in swarm mode), but you probably don’t need to know this unless you use Swarm.