First off, where is the documentation for developers?

I'm trying to display items under the subcategories located on the parent category page

Product category

Subcategory one
item
item
item

And so and so forth.

I've gathered that I'd have to do this with a little PHP, fine.

Unfortunately I'm having a hard time coming up with the syntax to piece this together.

I'm basically trying to get a foreach loop that loops through every item in a subcategory and spits out the title (that's all I need) however from what I can see I am not pulling in data so I would assume $subCategory->item->name isn't valid syntax.

Is there some type of documentation I can refer to, not necessarily for my issue but just to get an overview of the ins and outs of Joomla K2?

Thanks!