Docker is "an open-source project to package, ship, and run any application as a lightweight container." The idea is to provide a complete abstraction layer that allows developers to "containerize" or "package" any application and run it on any infrastructure.
Docker is a container-based software framework for automating application deployment. The “containers” are encapsulated lightweight and portable application modules.

*Installation of Docker

apt-get update
apt-get -y install docker.ioLink and fix paths with the following two commands:

ln -sf /usr/bin/docker.io /usr/local/bin/docker

sed -i '$acomplete -F _docker docker' /etc/bash_completion.d/docker.io

*Configure Docker to start when the server boots:

update-rc.d docker.io defaults

Source: Docker Tutorials