What is a Docker image?

A Docker image is a tool that aids in the creation of Docker containers. The build command may be used to generate a Docker image, which creates a container that starts when it starts to run. The Docker registry, such as the public Docker registry, stores all of the Docker images. These images contain a small number of layers inside them, resulting in a little quantity of data on the network.

A Docker Image is the template (application plus required binaries and libraries) needed to build a running Docker Container (the running instance of that image).

As templates, images are what can be used to share a containerized applications. Collections of images are stored/shared in registries like Docker Hub. When you download an image, it can then be used (as a template) to spin up multiple running Containers in your own environment.