• API Server is a core of the Kubernetes control plane. 
• The API Server exposes an HTTP API that lets end users, different parts of your cluster and external components communicate with one another. 
• API Objects in Kubernetes:
  • Pods
  • Namespaces
  • ConfigMaps
  • Events
• The Kubernetes API lets you query and manipulate the state of API objects in Kubernetes. 
• Operations:
  • Most of the operations in Kubernetes is performed through kubectl or kubeadm. 
  • This in turn use the API. 
  • However, you can also access the API directly using REST calls. 
• Clint Libraries:
  • If you want to use Kubernetes REST API (API Server), you do not need to implement the API calls and request/response by yourself. 
  • You can use the client library for the programming language you are using.
  • Client libraries often handle common tasks such as authentication for you. 
  • Most client libraries can discover and use the Kubernetes Service Account to authenticate if the API client is running inside the Kubernetes cluster
• Persistence:
  • Kubernetes stores the serialized state of objects by writing them into etcd.