wtf is Docker?
Docker is an open-source project to easily create lightweight, portable, self-sufficient containers from any application. The same container that a developer builds and tests on a laptop can run at scale, in production, on VMs, bare metal, OpenStack clusters, public clouds and more..
Learn more at docker.io
Docker is great for local development as well!
When you are ready to explore new programming language or need to setup a particular environment for a new application, but don't want to mess up your existing workstation with bunch of new dependencies, conflicting libraries and packages - run the whole thing inside of Docker container. It's like a private sandbox, that you can share with other developers and beyond, with all the environment already packaged in..