The XenServer PV Bus Windows Driver is a device driver used to enhance the performance of Windows virtual machines (VMs) running on Citrix XenServer or its successor platforms (like Citrix Hypervisor). The "PV" stands for Paravirtualization, which is a technique to improve the performance and efficiency of VMs by allowing the guest OS to communicate directly with the hypervisor without needing full hardware emulation.

The PV Bus driver enables higher-performance disk and network operations on Windows VMs by providing optimized drivers for these virtual devices. It allows Windows guests to utilize the paravirtualized block and network devices provided by XenServer. This is often required when using a XenServer-based virtual machine with a "paravirtualized" (PV) setup rather than a fully emulated device setup.