Customizing Dynamo package structure

I’m trying to create/publish a package, and trying to make all the custom nodes more organized. For example: in Clockwork Package, all the nodes are organized by different categories/functionalities. I did do some research and it seems like .dll or maybe .xml files in bin folder are the keys. Can anyone explain how to do this and how this works? Thanks a lot!

Right click on one of clockworks nodes > edit properties and you can see his structure.

Thank you John, that answered my question perfectly.