Docker is an open-source engine that automates the deployment of any
application as a lightweight, portable, self-sufficient container that will
run virtually anywhere.

Docker containers can encapsulate any payload, and will run consistently on
and between virtually any server. The same container that a developer builds
and tests on a laptop will run at scale, in production*, on VMs, bare-metal
servers, OpenStack clusters, public instances, or combinations of the above.