Nobody usually says 'glass windows' because all windows are made of glass! We normally just say 'windows'. 'French windows ' aren't windows. They are actually glazed doors, usually leading out into a garden or patio. I think that 'French windows' is mainly a British usage, as the US members seem to be more familiar with the term 'French doors'. I hope that helps.

If I remember correctly, French Windows open like doors but they have glass top to bottom. Sometimes they're incorrectly called French Doors.

I think french windows are a type of the general meaning of windows. These are more specific, with bars in the middle.

It is much more common to speak about "French doors" - which are in effect very long windows that are really doors. I am not sure that I have heard of "French windows". I suspect it is not a very hard definition and may vary between designers notes: "glass windows" is rare - the assumption is that windows are glass "French" does not mean you will find the answer in France - English often changes such meanings