TopoDS_TShape and TopoDS_Shape

i know, the TopoDS_Shape is the package for the entities topoligical of OCC. but i don't understaned the difference betwen Topods_Shape and Topods_Tshape.

and if i'd like to import OCC shape in another CAD ,i can point in TopoDS_Shape or in TopoDS_TShape for Topoligical entities.

how i'can connect OCC with another CAD.

think you;