Most fonts are created with quadratic Bezier curves, I think.

TheRealPomax · on Dec 28, 2014

Only OpenType with TrueType outlines (the common .ttf file) do - lines and quadratic curves is all you get. OpenType fonts with CFF/Type2 outlines (the equally common .otf files) use cubic curves instead, with an insanely rich instruction language for much better shape control.