It is too simple to give a complex diagram.
When Universal email is applied to your page.
1) It adds two library files. The first library file for the mail functionality and a general include file for formatting the email body and email address values... the contents of these files never change.
2) An include file is added where your mail settings and body are built... this is where all of your configured options are added and the file is named after the page where the universal email was applied.
What specific data do you not understand why it would be needed? Perhaps I can explain.