Kubernetes namespaces allow users to logically partition resources within a cluster, providing unique scopes to prevent name collisions, enforce policies for user access, and specify resource consumption constraints. By default, resources are created in the "default" namespace, but users can create additional namespaces with distinct resource constraints. These namespaces enable multiple groups to share a cluster while maintaining different quality of service levels, ensuring resources from one namespace are hidden from others. The "kube-system" namespace is reserved for internal Kubernetes resources. Users can create resources in specific namespaces and apply resource quotas to limit CPU and memory usage, ensuring efficient resource allocation. Resource quotas and limits must be configured to prevent pods from consuming all available resources, and limits can also be specified during pod creation for effective resource management. Overall, namespaces, resource quotas, and limits are essential for managing and optimizing the resource use of Kubernetes clusters across multiple environments.