Docker containers and images are two building blocks of the Docker platform. Docker containers are the running instances of the application. Containers are a runtime instances. They are lightweight, portable and can be created in any environment. Docker images on the other hand is the blue print that is needed to create the containers. Docker images are static, they don’t change, they are immutable. They are the source code of your application, they describe how to create and run an application. You can create as many instances of your application as you want using the single source code.