Kubernetes is an open-source container orchestration system used for managing and deploying containerized applications. A K8s cluster consists of master nodes and worker nodes. Master nodes host the control plane components responsible for management and orchestration, while worker nodes run pods containing containers. Key components of a K8s cluster include API server, scheduler, controller, Etcd, cloud controller manager, kubelet, and kube-proxy. Understanding these components is crucial for effective operation, management, and troubleshooting of the cluster.