What OS can run other operating systems inside itself while running on bare metal?

Question

Operating Systems

I really need to find an operating system that is similar to the "VirtualBox" program in its interface, and performs the same functions, only not as a program, but as an OS. Example: Windows, Linux and MacOS are running on my PC at the same time, and I freely switch between them.
(Preferably a full explanation, for hyper-dummies)

Answer 1

Proxmox
KVM
ESXI
XEN
Hyper-V