In Blender’s Freestyle, a line set filters which edges are drawn using criteria like visibility, face marks

https://hawara.net/index.php/How_to_Estimate_Material_Needs_for_an_AC_Line_Set_Job

In Blender’s Freestyle, a line set filters which edges are drawn using criteria like visibility, face marks, and material boundaries, allowing separate stroke styles for silhouettes and creases.