Orchestration systems like Kubernetes, Amazon ECS, and (formerly, it’s pretty dead) Mesos run on a cluster of systems and coordinate over the network. What they’re coordinating is running your containerized services, for example your API server, micro services, etc. So you can tell the orchestration service “run 5 copies of this and listen externally on port 9000. When a request comes in on external_ip:9000, redirect it to one of the 5 service instances.” They will also restart your services if they die, keep stdout/stderr logs, and so forth. You can have very complex setups but most will never need more than what I’ve just described.

The main difference between the different orch. tools is how they pipe the data between Outside and the service cluster. Mesos didn’t help you, you had to build your own service discovery. ECS uses Amazon load balancers and some custom black-box daemons. Kubernetes famously uses a complex mesh of “ingress controllers” and kernel iptables/ipfw spoofing. All take their configurations in some form of JSON or YAML.