YUM vs. RPM

From an article I found while Googling "how to create YUM packages":

"yum sits on top of rpm, and handles dependencies. For example, say you want xpdf. You get the package for xpdf and try to install it. rpm whines that it has an unsatisfied dependency, say some library you've never heard of (part of openmotif, but you don't know that), and gives up. You go get the appropriate package(s) and try again. This can get to be a pretty deep recursive process.

The program yum handles all that for you. You type at the command line:

# yum install xpdf

The program then pulls what it needs from the repository, figures out the dependencies, tells you what it needs to do to install xpdf, and asks permission to go ahead, like so."