The cluster: control plane & nodes
The two halves of every cluster.
In plain terms
A cluster is a restaurant. The control plane is the manager and the order book — it decides and remembers. The worker nodes are the kitchen — they do the cooking. Kubernetes is how the two coordinate.
A cluster is a group of machines working together as one. Those machines split into two roles: the control plane (the brain that decides and remembers) and the worker nodes (the muscle that runs your containers). You talk to the brain; it tells the muscle what to do.
Control plane — decides & remembers
API server
the front door you talk to
the store
remembers desired state
the brains
schedule + keep promises
Worker nodes — run your app
kubelet
starts your containers
your pods
the app, running
You almost never log into a worker node. You talk to the control plane’s front door (the API server), and it handles the rest.
That separation is on purpose: a busy app on a worker can never crowd out the brain that keeps the cluster running. As a beginner you mostly care about one thing — how to talk to the control plane. That is the next topic.