A Kubernetes cluster is a group of machines that work together to run applications.

It has two main parts:

This is the “brain” of Kubernetes.

It manages:

• Scheduling
• Scaling
• Health checks
• Desired state

Key components:

• API Server → entry point for all commands
• Scheduler → decides where pods run
• Controller Manager → ensures desired state
• etcd → key-value database storing cluster state

These are the machines that run your applications.

Each node contains:

• kubelet → agent that communicates with control plane
• container runtime → runs containers (Docker/containerd)
• kube-proxy → handles networking

Nodes run:

• Pods (your application containers)

The smallest unit in Kubernetes.

A pod:

• Contains one or more containers
• Shares network and storage
• Represents a single running instance

Example:

User → Service → Pod → Node

Control Plane decides:

• Where the pod should run
• How many replicas exist
• When to restart failed pods

Kubernetes cluster =

Control Plane (brain)
+
Worker Nodes (workers)
+
Pods (applications)