What is Docker Engine?

 The Docker Engine is the heart of the Docker platform, it consists of 2 main parts.
                The Client side (Docker CLI & Rest API) is used to fire commands
                The Server side (Docker Daemon) is used to process the commands and manages Containers.

The CLI uses the Docker REST API to control or interact with the Docker daemon through scripting or direct CLI commands. Many other Docker applications use the underlying API and CLI. The daemon creates and manages Docker objects, such as images, containers, networks, and volumes.     
 

Docker Engine supports the tasks and workflows involved to build, ship, and run container-based applications. The engine creates a server-side daemon process that hosts images, containers, networks and storage volumes. The engine also provides a client-side command-line interface (CLI) that enables users to interact with the daemon through the Docker Engine API.