what is cluster in kubernetes

A Kubernetes cluster is a set of nodes that run containerized applications. It is the basic unit of deployment in Kubernetes, and it allows containers to run across multiple machines and environments, including virtual, physical, cloud-based, and on-premises. A Kubernetes cluster is comprised of one master node and a number of worker nodes, which can either be physical computers or virtual machines. The master node controls the state of the cluster, including which applications are running and their corresponding container images, and it coordinates processes such as scheduling and scaling applications, maintaining the clusters state, and implementing updates. Each pod in Kubernetes is assigned a unique IP address within the cluster, allowing applications to use ports without the risk of conflict. All Kubernetes clusters should have cluster DNS, which is a mandatory feature that serves DNS records for Kubernetes services. The same API design principles have been used to define an API to programmatically create, configure, and manage Kubernetes clusters, called the Cluster API.