Hypervisors have certainly come a long way over the years. As of late, hypervisor vendors have gained enough traction in the market that they have wielded relationships with CPU and chip manufacturers such as Intel, AMD, and NVidia, in addition to the memory, storage, and network manufacturers. Today, when you go to buy a machine to run a hypervisor, there are built-in integrations between the hypervisor software and the physical hardware.
As of this writing, there are two types of hypervisors: Type-1 and Type-2. Also, there are four publicly available and usable hypervisors: VMware vSphere/ESXi, Citrix XenServer, Microsoft Hyper-V, and Linux open source Kernel Virtual Machine (KVM). XenDesktop is only supported on ESXi, XenServer, and Hyper-V, so we will limit our discussion to those.
No two physical server architectures are the same, and there is more than one server vendor. Some of these vendors you are familiar with, such as Hewlett Packard (HP), Dell, IBM...