Creating a subcategory of products

As you can see, their is this « New subcategory » button inside the « Our Houses » category :

If you click on this button you will go on the new category creation form page, and get exactly the same form than when you have clicked on the « New category » button previously.

You can create a category inside another category of products, that is indeed a subcategory. And a subcategory can itself contain some other subcategories, etc.