In various places on this site, you will see "XX.pretty".
Here's what I use that for….
KiCad (from sometime before vers 4-0-4) uses .kicad_mod files to hold footprint definitions. One file. One footprint.
The .kicad_mod files must be in folders with ".pretty" in the name, e.g….
(And yes, "MyFootprints.pretty" is all part of the name of a folder. In this context, the "." doesn't mean more than the "s" or the "p" beside it. "pretty" is not an extension, here, like, say, .txt, .exe, .lib.)
So… from time to time I need to say, in these pages, things like…
Put that in a folder that has ".pretty" as the last part of its name.
… which is a bit cumbersome. So I invented the usage….
Put that in an XX.pretty folder