Difference between Rancher and other container orchestration
[Rancher Labs employee]
Basically we are unopinionated about what orchestration system you want to use. Rancher contains our own container orchestration system called Cattle, which has a full UI, API, and supports YAML syntax that matches docker-compose plus additional things not available in compose.
Obviously we like our own but are aware that other choices exist in the ecosystem and many people want to use them. And managing their installations is not a trivial task... so Rancher contains (Cattle) templates for Kubernetes, Mesos, and Swarm.
When you create an environment you choose an orchestration system, and if you pick e.g. K8s we use Cattle to orchestrate the installation and configuration of K8s, plus integrating other Rancher services like access controls, load balancing, etc. You can then use the standard tools like kubectl, their API, or we have a fairly complete custom UI for K8s built-in.