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

https://wiki.familie-rosche.de/index.php?title=AC_Line_Set_Installation_Timeline:_What_to_Expect

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.