What is OTF?
OpenType with CFF outlines is what type foundries ship: cubic Bezier curves inherited from PostScript, plus the advanced typography tables that make ligatures and alternates work. Structurally it is a TrueType file with a different flavour tag and different outline data.
What is WOFF?
WOFF is a font wrapped for the web - the same TrueType or OpenType tables, each compressed, in a container browsers fetch happily. That is the whole format, which is why converting between WOFF and TTF or OTF is lossless repackaging rather than a redraw.