I will ask something that maybe looks like a fundamental question, but I believe it is quite essential for young font engineers/devs/(type)designers like myself who knows a little about the history behind OTF and TTF.
I've been curious what really makes the difference between those two extensions. Especially when it comes to Variable Fonts, is it just a type of curves? Or is there any other differences? Or maybe is it just another reminiscence of so-called "font wars" without any particular meaning? Or is there any differences in hinting implementation?
In what circumstances is it recommended to use "otf" and "ttf" variable fonts?
Is there some particular reason why I usually see variable fonts with ",ttf" extension?