What Are Shells?
Shell is a program that is responsible for executing the command provided in the command prompt. It breaks down the command into smaller units called tokens and then executes them. It is an interface between the operating system and the user. The command prompt takes input from the user and gives it to the shell to execute it and the shell then returns the response to be displayed on the command prompt.
Docker – Containers & Shells
Docker is a set of platforms as a service (PaaS) products that use Operating system-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries, and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating system kernel and therefore use fewer resources than a virtual machine.