VMware ESXi is an Operating System and a VMware proprietary. It is a Hypervisor that is designed on VMkernel platform. ESXi hosts offers physical resources(CPU, Memory, NIC or local HDD) to running Virtual Machines on it. Virtual machines can have different OS or different set of Apps.
Few more facts about ESXi Hosts:-
- ESXi hosts are managed through an interface which is BIOS-like console or through vSphere Command Like Interface (vCLI).
- ESXi hosts come as a Installable package or can be Embedded(in firmware, USB or inside a BIOS chip).
- ESXi hosts has a high security and a small disk footprint.
As, a recommendation we should install & configure ESXi hosts properly on supported hardware. All hardware can be verified by visiting VMware hardware Compatibility Guide. https://www.vmware.com/resources/compatibility/search.php?