The easiest way to understand the difference between an Image and a Container is to think about architecture blueprints versus an actual physical building.
The Docker Image is the blueprint. It is a read only file that contains the exact settings required to run your application. You can’t live inside a blueprint and it doesn't consume any power or CPU. It just sits on your disk as a master template.
The Docker Container is the actual physical house. When you tell Docker to run an image it reads the blueprint and instantly constructs the isolated environment on your server. The container is where your code actually executes
If you need to scale up your application to handle a massive spike in user traffic, you don't need to write new code or create a new template. You take that exact same single blueprint (image) and use it to stamp out 10 or 20 identical, running environments (containers) across your cluster in less than a second