The control plane is the coordinating brain of the cluster. It has a controller that manages nodes and services, a scheduler that assigns pods to the nodes, and the API service, which handles communication. Configuration and state are stored on a highly-available database called etcd.

The worker nodes are the machines that run the containers. Each worker node runs a few components like the kubelet agent, a network proxy, and the container runtime. The default container runtime up to Kubernetes version v1.20 was Docker.