Hypervisor-based might be the most common form of server virtualization in organizations, but there are other options to consider, including hardware-assisted and OS-level
"With virtualization, the network, storage and compute resources are abstracted, so applications, services and functions are less dependent on the physical hardware. IT administrators can provide applications, services and functions with their own environment -- which includes an operating system, support software, network and storage resources -- that is less prone to problems caused by other workloads running on the same underlying resources. Or they can share resources to reduce cost and improve overall utilization and performance..."