I will talk about this, noting that "FON" has become a somewhat common file extension for several different font formats. Of course, the most common are Microsoft, but there are other files that call themselves FON, which use a completely different format. Therefore, you can double check this. The information that I include below applies only to the Microsoft format.
FON is actually just an EXE format, that is: FON files are EXEs that contain font resources (and only font resources), renamed with the FON file extension. For more information about it, see this very old documentation, written around the time FON was introduced .
, , FNT. Microsoft .
, FNT, , Windows ( FNT FON, , , FON).