Here is an outline of what I am planning; the article will be centered
around a number of "frequently asked questions":

1) What is a "font family"?

2) What are the "default font families" in LaTeX?

3) How can I change the font in certain parts of my document,
   such as section headings, captions etc?

4) How can I change the defaults for a complete document?

5) Which alternatve font families are available in my LaTeX
   system at all?

Section 1 will, of course, not go into the implementaion details, but
it is necessary at least to avoid confison.

Sections 3 and 4 will focus on a few examples; beyond that, they will
guide the reader to the existing documentation of classes and packages.

Section 5 can hardly give any answers at all; instead it will be just a
"guide" to the documentation. Yet I do not want to omit this question,
because it comes up too frequently.