EDIT: Updated the link
Rendered at:https://60897-1385122-gh.circle-artifacts.com/0/doc/build/html/users/fonts.html
(needs proper linking from user's guide)

This seems helpful. Is this where you decided it belongs? Most other font info is in tutorials, and users seems to have become a dumping ground for random bits like this.

I think for some of the more technical details we should link out to more definitive resources rather than become bogged down in rewriting the specs for each type of font.

I think it would be helpful to give some examples of what type of fonts correspond to what type of downloads (briefly). i.e. some of those fonts are always available (Type 1)? Many are often present on systems (TrueType?) or more commonly downloaded. I appreciate this is complicated, and I don't think you need to go into laborious detail, but I think this guide could be more practical for the end user as opposed to developers.

I think it would be helpful to give some examples of what type of fonts
correspond to what type of downloads (briefly). i.e. some of those
fonts are always available (Type 1)?

Right, so there is one more kind of font that is always available
without downloading but is of limited use: PostScript interpreters and
PDF consumer applications must have a set of predefined core fonts
available. Matplotlib calls them "AFM fonts" which is a bit of a
misnomer, since AFM is a format for font metrics. The reason is that
Matplotlib distributes only the metrics needed for rendering these
fonts, and the viewer application supplies the glyph definitions.

I believe this applies to the 14 PDF core fonts but am not sure what the
PS backend does. It seems that recent versions have many more built-in
fonts:

https://en.wikipedia.org/wiki/PostScript_fonts#Core_Font_Set

The downside of using "AFM fonts" is that they cannot be rendered in
other backends.

I believe Type 1 fonts mainly enter the system via usetex/dviread, but
you could probably specify a pfa file in plotting commands and it would
work.

Many are often present on
systems (TrueType?) or more commonly downloaded.

Also present on the system are the old MacOS resource-fork fonts and the
newer OpenType fonts, which are basically TrueType with extensions. I
don't think Matplotlib supports either.

A related question that I don't immediately know the answer to is how
the search path for fonts is specified and which operating-system
facilities are used for font lookup.

The reason is that
Matplotlib distributes only the metrics needed for rendering these
fonts, and the viewer application supplies the glyph definitions.

I believe this applies to the 14 PDF core fonts but am not sure what the
PS backend does.

It's still recommended to embed some version of the core fonts if you're using them, and I believe we do. That's toggled by the pdf.use14corefonts rcParam:

Ah, for PostScript, non-embedding might be triggered by ps.useafm.

This seems helpful. Is this where you decided it belongs?

Yeah, @tacaswell pointed out we could model it after this user guide.

And I think it's at the right place, since all other information around fonts is more on the technical side: "how to use/modify this font with Matplotlib?" vs "okay what does Matplotlib has to do with fonts at all?"

As discussed on the call, it is easy to find more things to add, but this definitely passes the bar of "is it better than before?".