KVM
https://www.linux-kvm.org/
Using KVM, one can run multiple virtual machines running unmodified Linux or Windows images. KVM is open source software. The kernel component of KVM is included in mainline Linux, as of 2.6.20.
Kernel-based Virtual Machine - Wikipedia
https://en.wikipedia.org/wiki/Kernel-based_Virtual_Machine
Kernel-based Virtual Machine (KVM) is a virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It was merged into the mainline Linux kernel in version 2.6.20, which was released on February 5, 2007.
What is KVM?
https://www.redhat.com/en/topics/virtualization/what-is-KVM
How does KVM work? KVM converts Linux into a type-1 (bare-metal) hypervisor. All hypervisors need some operating system-level components—such as a memory manager, process scheduler...
KVM/Installation - Community Help Wiki
https://help.ubuntu.com/community/KVM/Installation
To run KVM, you need a processor that supports hardware virtualization. Intel and AMD both have developed extensions for their processors, deemed respectively Intel VT-x (code name Vanderpool)...
Welcome to KVM virtualization - Thorough introduction
https://www.dedoimedo.com/computers/kvm-intro.html
KVM functions by utilizing the CPU virtualization technology extensions on modern Intel and AMD KVM - Pros and cons. Should you use KVM? Well, that depends what you want to achieve.