Hypervisor

A hypervisor is the software layer that lets multiple virtual machines share a single physical host. There are two types: Type-1 (bare-metal, runs directly on hardware: ESXi, Xen, Hyper-V) and Type-2 (hosted, runs on top of an OS: VirtualBox, VMware Workstation). KVM is technically Type-1 because it's part of the Linux kernel running directly on hardware; from the user's perspective, it has Type-2 ergonomics.

For offshore hosting customers, the hypervisor choice rarely matters at the application level — your VPS behaves like a Linux box regardless. Hypervisor differences become visible when: (a) you want to run nested virtualisation (works on KVM with vmx flag enabled, partial on Hyper-V), (b) you need PCI passthrough for GPUs / specialised hardware, (c) you're benchmarking microseconds for HFT-style workloads.