This question comes up frequently on the Linux_Newbies list. There are various commands that work, so if you’ve heard something different, and it works well for you, then use it. There are variations of commands that one person, such as myself, uses more out of habit than anything else.
RPMS are packages compressed using the RedHat Package Manager (ergo, R P M). Both KDE and Gnome have graphic interfaces for installing RPMS, however, some folks seem to have difficulty using them and of course, one feels more like a Linux ace if they install via command line.