Fonts marked TT and O

[Vance Roos]

What is the difference between fonts marked with a TT or an O icon?

I guess TT stands for "truetype" which I gather has superior scaling
capabilities.

What about the O fonts? And are they better or worse than TT fonts?

 

[Donald F. Luchini]

TT and O fonts are actually the same thing. The only difference is that O
fonts are required by Windows to run correctly and cannot be removed, and TT
fonts are optional and can be removed.