A Feature (pointer on Dtk_feat) can be a construction or a manufacturing feature.
Parameters can be used in downstream applications (holes, patterns, threads, pockets and others depending on the CAD format).
It can be associated with any Dtk_Node type in the construction tree.
Feature read is only available from :

CATIA V5
CATIA V6
NX (Unigraphics)
SOLIDWORKS
Creo Parametric (Pro/Engineer)

Feature reading needs a specific licence.
All metric data in feature classes are given in millimeters (MM).
All angular data are given in degree.

To have detailed information for using features methods to access data of specific features, namely "Hole", "Thread" and "Pattern", you can refer to the following page:

Calling Feat methods

See Feature mapping in readers menu :
Readers Mapping