Open or Closed

Open entities: These include lines, paths and arcs. A width 0 open entity does not exhibit a fill style; neither does a width 0 path. If you give an open entity a width, you can see the fill style in the edge.

Closed entities: These include polygons, smooth polygons and circles. If these have a width of 0 then they will fill completely with a fill style. If they have a width of greater than one, only the boundary will fill.