“…Docker started as just a software container on top of a Linux operating system. Its disruptive force however comes from the fact that it does force us to rethink many of the layers of the cloud stack. Starting from the way we handle configuration management, through the way we handle networking and build systems, and even microservices. Not all of this is directly related to Docker per se, but that’s the difference between thinking of Docker as a container, and Docker as a change agent or a movement…”

Here you can read more about PaaS vs Docker.