Moodle community sites

Hi all ,
I am on a project involving development for moodle.
And the company also wants to make the patches open source.
And now , I have browsed through , but maybe I missed something ,
I guess there is no introduction to the design tree or what page does what ,
or what is the general framework . I hope developers understand what I mean .

Can someone help me with this , or should I do this myself , by going through each page and block defined in index.php ?

Thanks in advance
Antano Solar John