Yum is a package manager for Linux systems that rose to prominence for being the default package management system for Red Hat Enterprise Linux and its derivative distributions for many years. It has since been replaced by dnf package manager, which is a fork of yum that has been developed to be faster, more efficient, and have better documentation. Modern Linux distros only use yum as a compatibility layer for dnf, in order to accomodate legacy Bash scripts and old commands.
This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-install-yum-on-linux