The Divi theme documentation is quite extensive and well thought out to give you an easy introduction to the theme and its various elements. The main Divi theme documentation page lists The Divi Basics, The Modules, Additional Features and the Elegant Themes Basics.
These should help you get all the basics understood and so make sure you check out all the info to get a good idea of how the Divi theme works. If you need more help than what is available in the Divi documentation, check out the excellent Elegant themes support forums, or the FB group for Divi users. Below is the Divi theme documentation and the first place you should look for learning about the Divi theme.