vtb to otf conversion is almost certainly used for the purpose of converting fonts, to be more specific betwen FontLab's VFB format and OpenType OTF fonts.
Considering that .vtb files come from Fontlab Studio, it's the obvious tool for such export, but both formats are nowadays supported in many other font software, so it should not be hard to find one that can help you convert vfb to otf or even vice versa.
Updated: August 17, 2023