What tools do hosting companies use to share space?

Question

Virtualization

I suppose from the title the essence of the question becomes transparent - with the help of what tools do hosting companies create shared space on one physical machine?
Virtual machines, if so, which ones, docker, or other proprietary technologies?
And I would like to hear how you can organize a similar free software environment.

Answer 1

Try libvirt/QEMU/KVM

Answer 2

For one server, ESXi will go - it is free for one server (well, that is, it will be free for a dozen hosts, only they cannot be combined into a sphere).
You can use KVM (qemu + libvirt) - for example, proxmox works on it