Hi!
  It’s not a mess IFS has divided some modules into two parts.
One of them is a part where are form’s/class that can be used in other modules (external part)
The second of them is a part where are form’s/class that can be used only inside this module.
It was created to generate a smaller dll library, and to faster loading after clicking on some of the forms in the navigator. 
When you click on some of the form in the navigator, form for example from module ORDER you can see that application loads another module (for example INVOICE). In that case, the application loads this external part of the INVOICE module. The whole module INVOICE can be large, but we load a small part of them, not the whole module.
Best regards,

Szymon Grzegorczyk

Hi @KNESZYGRE,

This answer is good enough for me. Thank you for the explanation.