• A Docker image is a file used to execute code in a Docker container.
• Docker images act as a set of instructions to build a Docker container, like a template.
• Docker images also act as the starting point when using Docker.
• An image is comparable to a minimal lightweight snapshot in virtual machine (VM) environments.
• Docker image contains application code, libraries, tools, dependencies and other files needed to make an application run.
• When a user runs an image, it can become one or many instances of a container.
• Docker images have multiple layers, each one originates from the previous layer but is different from it.
• Image layers are also read-only files. Once a container is created, a writable layer is added on top of the unchangeable images, allowing a user to make changes.
• A Docker image has everything needed to run a containerized application, including code, config files, environment variables, libraries and runtimes.

• The docker run command creates a container from a specific image.