Basic data types

Hi~

I want to progamm add-on application of gear hobbing using the CoCreate/SolidDesigner Integration Kit.

But I met some questions about the basic data types in Modeling sofeware environment.

Just like point (gpnt3d or gpnt2d),  direction ,  vector , position , u-vector , gpntwc , etc.

Does anybody could help me to explain them , and what difference between them?

Thanks

Justin