Final answer:
A server dedicated solely to running virtual machines without any other applications is using a Type 1 hypervisor, which runs directly on the host's hardware.
Step-by-step explanation:
If you are running virtual machines on a single physical server where the server operating system is solely dedicated to virtualization and does not run any other applications, the type of hypervisor being used is known as a Type 1 hypervisor. This kind of hypervisor runs directly on the host's hardware to control the hardware and to manage guest operating systems. This arrangement is in contrast to a Type 2 hypervisor, which runs on a conventional operating system just like any other software application.