Docker is a software project that implements lightweight containers on top of the Linux operating system. Docker containers are similar to virtual machines in terms of isolation of packaged applications, but they are lighter and easier to maintain and deploy.
Docker can be integrated into several cloud services providers such as Microsoft Azure, Amazon Web Services, Google Cloud Platform, Jenkins and Puppet. A lot of applications and development environments have been dockerized, which means that a docker container with the respective application or technology already installed and provided by official or third party sources. A few examples of official containers: