what is polyline

[Markus Spring]

Hi

I tried to figure out what exactly is polyline.
Is it true that

* I can just display the outlines of a polygon rendered with a specified
line symbol
* but can not display polygons with fill and a specified outline

If yes, then I don't know what's the difference to using TYPE LINE for a
polygon shapefile.

Any explanation, maybe example would be appreciated.

Kind regards - markus