Screen printers sometimes wish to have one color print on top of another to create a secondary color or special effect. Also handy when creating an under base screen.
Select a shape that is positioned over (or overlap) a portion of another shape. From the Edit Menu choose Overprint Outline or Overprint Fill.
Corel shows you the effect on screen.
Shapes that have overprint assigned to them allow the shapes below to print entirely rather than knocking out the shape at the time of separation creating "butt" "registration".
By default a vector program is set up to handle shapes on the WYSIWYG (pronounced: Wizzy Wig), it stands for "what you see is what you get". The over print feature changes that allowing over lapping shapes to print the shape below. This way you can place a shape directly on top of another, assign over printing, and go to the print window only one time to print all your separations including a base screen. No more back and forth to the workspace to change colors or move shapes like we did "pre computers".
Work smarter not harder, that's why you have these programs and a computer. Know your programs and use the features properly.