Hi Pilou,
Imagine a cube sliced into 2 parts by the script. That's all it is, just a quick convenience function to slice and dice an object up real fast. One use for it is if you have a model with internal parts and want to get a quick look at something inside - split the model, take a quick look, hit undo and you're back to where you started. Another use might be to make a quick cross-section of a model or to chop a section out of a model by splitting the model in 2 places and deleting the section.
Hope that helps!

Paul