With container-based development, deployment, and the whole ecosystem, following are the key concepts to understand the modern day containerization:.

• Container host: An operating system on a physical machine (bare metal), or a virtual machine configured with the container support.
• Container OS image: Containers are deployed from images in the form of layers as they stack up. The container OS image is the first layer in potentially many image layers for the given container. This image provides the basic required operating system environment for the desired application.
• Container image: A container image is primarily for the intended application, and it contains the base operating system, application, and all application dependencies in the form of container layers, as well as essential configurations that are needed to deploy a container.
• Container registry: Container registry is the placeholder for the container images which can be downloaded on demand. For example:
  • Docker Hub
  • Amazon EC2 Container Registry
  • Azure Container Registry
• Container repository: Container repository is a collection of different, but related, container images with different tags used to identify different versions of the same application or service.
• Configuration: Container configuration file is used to automate the creation of container images. It can, for example, specify the required base images, directory mappings, and required files before the given container is executed. For Docker-based container images, it is Dockerfile for all platforms.
• Container orchestration: When you deploy tens, hundreds, or thousands of containers that make up an application, tracking and managing the deployment requires sophistication in both management and orchestration of those containers. Container orchestrators are assigned a pool of servers in a cluster and the respective schedule to deploy containers onto those servers. Some orchestrators configure networking between containers on different servers, while some may also include load balancing, rolling updates, extensibility, and more. Examples of popular container orchestrators include the following:
  • Docker Compose / Docker Swarm
  • Kubernetes
  • Mesos / DCOS