Earlier quoted context omitted.
The FSF can explain it better than I can. https://www.gnu.org/licenses/license-list.html https://www.gnu.org/licenses/licenses.html
> It drives me nuts how much people talk about OSS when they need to at least mention the difference between FOSS and OSS. Maybe because like you they find it hard to explain? According to your linked resources, it appears that everything except the Common Clause is FOSS. So, basically everything I've ever seen is FOSS.
> So, basically everything I've ever seen is FOSS.
Correct. Free Software just puts more attention to the freedom part of software.
GNU has a nice diagram and some category definitions for software at https://www.gnu.org/philosophy/categories.html