This guide will teach you how to create and manage a VM in KVM using virt-install, virsh, and virt-viewer, which all make use of libvirt. For a beginner's guide and introduction to libvirt and virtualisation concepts, and why you would even want to use libvirt instead of, say, Virtualbox, see: https://jamesnorth.net/post/qemu-guide
Here's the scenario: your laptop is approaching 13 years of age, the internal NIC has suddenly stopped working, but you don't want to give up here. You uninstall Arch Linux and install Windows 10 just to check that the NIC is actually not functioning anymore—which it isn't. You buy a USB Wi-Fi NIC Adapter, carelessly not checking if the vendor's drivers have been mainlined into the Linux kernel. You boot into an Arch Linux live session and you don't have an internet connection. Here's what you do next.