Rancher is an open source software platform that enables organizations to run and manage Docker and Kubernetes in production. With Rancher, organizations no longer have to build a container services platform from scratch using a distinct set of open source technologies. Rancher supplies the entire software stack needed to manage containers in production.
In simple words, Rancher is a set of tools that help you easily deploy containerized environment. But unlike Kubernetes and other container orchestration tools, Rancher works on a higher level increasing the efficiency of other orchestration tools.