New to PHP and Web Assist products

I am new to PHP and Web Assist products in general, and am currently working on a project that uses Universal Email.

I am also like the 25% of the population that learns best in a Kinesthetic type way… essentially being able to take something that works apart and understand the:

“Why it does what it does”.

Would anyone here have basic diagrams of the PHP processes (relational to each file) in regards to Universal Email. The best way to explain it may be to show an example.
As here is one for Moodle's database:
moodle.png

Also, I have gone through the tutorials in support and training and none seem to explain why specific data is entered, as though there is an assumption of a knowledge of MySQL and PHP that I, and I am sure many others, do not possess (but wish desperately to).

Any help would be greatly appreciated.