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.
— Docker: the Linux container engine

It's essentially a friendly wrapper around the commands which implement the Solaris-like zones/containers on Linux. Given time, and some commitment from some devs and this could be a useful tool for Solaris zones too.