Path operations are sometimes called Boolean operations because they are based on Boole's maths. They are really well known in graphical applications. Adobe Illustrator knows them as Pathfinder and Inkscape has much more choice than Scribus in its Path menu. In Scribus they are not so easily accessible because they are rarely used. But they can sometimes be very useful.
You will use them when you need to have a more complex shape than a rectangle or a circle. Generally, you will use two or three basic shapes to make a new one by combining or subtracting them in a certain way and then using them as a background shape, text, or Image Frame.
The principle is really simple:
Draw two shapes.
Make them more or less overlap.
Use the Path operation window to combine them into one resulting shape.
Do what you need with that shape.
In Scribus, path operations will be available in a window that you can call from Item | Path Tools | Path Operations. Here, you will have several...