Kubernetes is a system for managing containerized applications across a cluster of machines. Kubernetes runs all applications in containers. In the default setup, this is performed using the Docker engine, but Kubernetes also features support for using rkt as its container runtime backend. This allows a Kubernetes cluster to leverage some of rkt’s security features and native pod support.
It is massively scalable tool for managing containers, made by Google. It is used internally on huge deployments and because of that it is maybe the best option for production use of containers. It supports self healing by restating non responsive containers, it pack containers in a way that they take less resources and has many other great features.