What is the Unit Standard use when you make a detail or section drawing?

I think it depends from office to another but of course the mm is the certain unit for detailing

For better accuracy mm is recommended

Most of countries use the "system international "or "SI" for drawing units, this is based on the metric system where all dimensions are measured in millimeters .Some parts of Europe still use the old European metric standard centimeters for drawing units.

In USA they still use the Imperial units (feet and Inches ) in all drawings.

Generally we use MM for detail dimensions 

In South Africa the unit that is used to design structures on Autocad is the mm,most engineering drawings consist of this unit.

In the Philippines we usually use "SI" commonly known as system international which is based on metric system. Mostly for detailed drawing we use millimeter as the basis for1 meter if being scaled.

the

 millimeter(mm)

for units go in settings select SI units and units selected should be in millimeters

the standard units when making a drawing is in millimeters(mm)

 it can either be millimeter (mm) or inches (in) depend upon the organizations which standard system they follow. 

What ever it may be2D or3D ,units are use as millimeters (mm)