Virtualization (QEMU).

In their own words, "QEMU is a generic and open source machine emulator and virtualizer." 

QEMU can use other hypervisors like Xen or KVM to use CPU extensions (HVM) for virtualization. When used as a virtualizer, QEMU achieves near native performances by executing the guest code directly on the host CPU. 

In simple terms, one can use a different opearating system on top of another operating system whilst achieving real hardware performance.

Another way to use QEMU is User Mode Emulation, where QEMU can launch processes compiled for one CPU on another CPU. In this mode the CPU is always emulated.

 The awesome thing is QEMU is supported on both Windows and Linux (including macos). In my personal experience it works best in Linux rather than windows.

 

Required packages for QEMU on Linux :

Arch:

 

sudo pacman -S qemu virt-manager virt-viewer dnsmasq vde2 bridge-utils openbsd-netcat ebtables iptables libguestfs

Debian:

sudo apt install qemu-kvm qemu-system qemu-utils python3 python3-pip libvirt-clients  libvirt-daemon-system bridge-utils virtinst libvirt-daemon virt-manager

For full setup of QEMU refer to - 

1. https://wiki.archlinux.org/title/QEMU

2. https://christitus.com/vm-setup-in-linux/

Windows:

The windows installation is a bit tricky since it requires you 

to partition your drive and install it on that partition as you 

would an operation system.

A comprehensive guide for windows can be found at

 https://www.minitool.com/partition-disk/qemu-for-windows.html 

In conclusion QEMU allows you to run different OS's on a single host machine

 without any performance bumps so it is a great alternative to dual booting. 

The one thing to keep in mind is it uses large amount of system resources. 

So it may affect system with low specs negatively.