The Main Pillars of Kubernetes

When Kubernetes is deployed a cluster is created. This cluster consists of two main components. The control plane and the worker machines called Nodes.

Source: kubernetes.io/docs/concepts/overview/components

The control plane

The control plane, shown on the left, stores the cluster's desired state and coordinates changes. Its controllers respond when resources differ from that state, such as when a Deployment needs more replicas. The scheduler chooses a node for each new Pod.

In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.

Nodes

Kubernetes runs your workload by placing containers into Pods and these Pods run on worker node(s). A node may be a virtual or physical machine, depending on the cluster. Each of these nodes is managed by the control plane and contains the services necessary to run Pods.

Each node uses a container runtime and a kubelet agent to run its assigned Pods.

Typically you have several nodes in a cluster; in a learning or resource-limited environment, you might have only one node.

Kubelet

The Kubelet is a part of the Node. It is an agent which runs on every node. It makes sure that Pods on the node have running containers. It monitors the Pods and makes sure they are running according to their PodSpec.