Docker is a computer platform that acts as a virtual machine that acts as an operating system. It was created by Docker Inc. and was primarily made for the Linux system. This is because it will use some of the resources that are built into Linux to enhance its features.
Docker was started in France by Solomon Hykes as a project within another called dotCloud which was a platform as a service company. Essentially Docker represents an evolution of the dotCloud technology which itself was birth from an open source projects named Cloudlets.
