Docker is Open Source software. It provides the automation of

Linux application deployment in a software container.

We can do operating system level virtualization on Linux with

Docker.

Docker can package software in a complete file system that contains

software code, runtime environment, system tools, & libraries that

are required to install and run the software on a server.

https://www.docker.com/

Docker is a software platform that allows you to build, test, and deploy applications quickly. 

Docker packages software into standardized units called containers that have everything the software needs to run including libraries, system tools, code, and runtime. 

https://aws.amazon.com/docker/#:~:text=Docker%20is%20a%20software%20platform,tools%2C%20code%2C%20and%20runtime.