The four major components of DOCKER are daemon, Client, Host, and Registry

• Docker daemon: It is also referred to as ‘dockerd’ and it accepts Docker API requests and manages Docker objects such as images, containers, networks, and volumes. It can also communicate with other daemons to manage Docker services.
• Docker Client: It is the predominant way that enables Docker users to interact with Docker. It sends the docker commands to docked, which actually executes them using Docker API. The Docker client can communicate with more than one daemon.
• Docker Registry: It hosts the Docker images and is USED to pull and push the docker images from the CONFIGURED registry. Docker Hub is the public registry that anyone can USE, and Docker is configured to look for images on Docker Hub by default. However, it is always recommended for organizations to use own private registry.
• Docker Host: It is the physical host (VM) on which Docker Daemon is running and docker images and containers are created.