Kubernetes supports multiple virtual clusters backed by the same physical cluster. These virtual clusters are called:

Namespaces in Kubernetes provide a mechanism for isolating groups of resources within a single cluster, serving as virtual clusters for different teams or projects. This allows for resource organization and access control, ensuring that resources in one namespace do not directly conflict with resources in another, without requiring separate physical clusters.

Containers are the isolated environments where applications run, not virtual clusters themselves.

Hypervisors are used in virtualization to create virtual machines, which is a different concept than Kubernetes virtual clusters.

cgroups (control groups) are a Linux kernel feature for resource management and isolation for processes, not Kubernetes virtual clusters.