Meet other developers and ops engineers using Docker. Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications. Consisting of Docker Engine, a portable, lightweight runtime and packaging tool, and Docker Hub, a cloud service for sharing applications and automating workflows, Docker enables apps to be quickly assembled from components and eliminates the friction between development, QA, and production environments. As a result, IT can ship faster and run the same app, unchanged, on laptops, data center VMs, and any cloud.
But where to file it? Languages? No. Hardware? Nope. Applications? Maybe. I'll put it under Operating Systems since it's more SysAdmin-ish.