For when you want to repeat a selection throughout your image
You can tell it to repeat Vertically/Horizontally every X pixels with an offset number pixels in the other direction.

https://gimplearn.net/viewtopic.php?f=3&t=2430#p27026

This looks cool. I would love something like this but with a matrix selection that includes x and y offsets, resizing, opacity etc so that, for example, you could create spiral cloning and perspective cloning.