When you use the Vector tool from the Tools Toolbar you can draw all sorts of shapes e.g. Squares, Circles and Irregular shapes – these shapes are Polygons.

Below, left, is the Vector – Car object. This is made up of several Circles and Irregular shapes, which Opus calls Polygons:

On the right is an Illustration of part of the Objects tab in the Organiser showing the Vector object named Vector – Car: