Docker images are the basis of containers. An Image is an ordered collection of root filesystem changes and the corresponding execution parameters for use within a container runtime. An image typically contains a union of layered filesystems stacked on top of each other. An image does not have state and it never changes.
A Docker container is a runtime instance of a docker image.
A Docker container consists of:
- A Docker image
- An execution environment
- A standard set of instructions
The concept is borrowed from Shipping Containers, which define a standard to ship goods globally. Docker defines a standard to ship software.