I found here that Magento is using these tags as custom config variables, but I still cannot understand where are they used and how. For example the Wishlist module has wishlist (same name as the module) xml tag in the config.xml file in which it defines:

<item>
<product_attributes>

<visibility/>

<url_path/>

<url_key/>
</product_attributes>
</item>

Where is this module using these configurations? Also if I was to build payment method, I have to add in my custom module config.xml a tag for sales and then for quote and so on... I also found other related questions, but most of the answers were that these tags can be anything, but I need to know how they are used by the system. Thank you in advance