Docker Terminology - Basics

An image is a lightweight, stand-alone, executable package that includes everything needed to run a piece of software, including the code, a runtime, libraries, environment variables, and config files.
container is a runtime instance of an image—what the image becomes in memory when actually executed. It runs completely isolated from the host environment by default, only accessing host files and ports if configured to do so.
Containers run apps natively on the host machine’s kernel.

Docker daemon - The background service running on the host that manages building, running and distributing Docker containers.
Docker client - The command line tool that allows the user to interact with the Docker daemon.
Docker Store - A registry of Docker images, where you can find trusted and enterprise ready containers, plugins, and Docker editions. You'll be using this later in this tutorial.

An important distinction with regard to images is between base images and child images.
·         Base images are images that have no parent images, usually images with an OS like ubuntu, alpine or debian.
·         Child images are images that build on base images and add additional functionality.
Another key concept is the idea of official images and user images. (Both of which can be base images or child images.)
·         Official images are Docker sanctioned images. Docker, Inc. sponsors a dedicated team that is responsible for reviewing and publishing all Official Repositories content. This team works in collaboration with upstream software maintainers, security experts, and the broader Docker community. These are not prefixed by an organization or user name. In the list of images above, the pythonnodealpine and nginx images are official (base) images. To find out more about them, check out the Official Images Documentation.
·         User images are images created and shared by users like you. They build on base images and add additional functionality. Typically these are formatted as user/image-name. The user value in the image name is your Docker Store user or organization name.
A registry is a collection of repositories, and a repository is a collection of images

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