Control plane: API server (entry point), etcd (state store), scheduler (assigns Pods to nodes), controller manager (reconciliation loops). Worker nodes: kubelet (node agent), kube-proxy (networking), container runtime (Docker/containerd).

The API server is the single gateway for all cluster operations - kubectl, controllers, and external tools all communicate with it. etcd stores the desired and current state as key-value pairs - it is the source of truth. The scheduler watches for unscheduled Pods and assigns them to nodes based on resource availability and constraints. Controller managers enforce desired state: if a Deployment wants 3 replicas and only 2 run, the replication controller creates the third.