It is a good idea to try to understand the basic roles of these entities. It will speed up learning on how you can work with them. One of the things many users stumble upon is the difference between a Docker image and a container.
This brief wiki will explain how the two differ, and also how they relate. Read more to find out.
Docker is a platform that runs each and every application segregated and securely by the use of kernel containerization feature. It is a highly efficient and lightweight platform in terms of resources it uses. It uses the host underlying kernel containerization feature rather than creating its own hypervisor.
Docker Image is a set of files which has no state, whereas Docker Container is the instantiation of Docker Image. In other words, Docker Container is the run time instance of images.