The VirtualBox USB Windows driver is a driver necessary for enabling USB device support in Oracle VirtualBox when running Windows as a host operating system. It allows VirtualBox to detect and interact with USB devices (e.g., USB flash drives, external hard drives, printers, etc.) that are connected to your Windows host machine.
By default, VirtualBox can support USB devices through its Extension Pack, but you may need to install the USB driver specifically if you want full access to USB devices inside your VirtualBox virtual machines (VMs).