It’s pretty easy in fact. Vanilla and BS stockpiles work the same way. Each time a Hearthling wants to pick up an item, he or she will look at it’s tags, and then will search for the closest stockpile with a filter corresponding to one or several tags.
Let’s pick up an item, a lump of coal, with the following tags:
"material_tags" : "stockpile_ore coal ore resource"
In the vanilla game, the “Ore” stockpile has the following filter:
"filter" : "stockpile_ore"
So this is where we can put our item! Because it’s tags contains the word “stockpile_ore”.
In BS, there are several “Ore” stockpiles:
"filter" : "stockpile_ore coal"
"filter" : "stockpile_ore copper"
"filter" : "stockpile_ore iron"
In this case our item will be put in the stockpile “Coal”. There is no more “stockpile_ore” filter, and the only matching filter is “stockpile_ore coal”.
Let’s take another item, with the following tags:
"material_tags" : "cloth armor light_armor stockpile_equipment"
Imagine we have two stockpiles with these filters:
"filter" : "stockpile_equipment cloth"
"filter" : "stockpile_equipment armor"
The item can goes in the two stockpiles, because their filters both match the tags. It’s a situation I try to avoid with BS!
Finally, let’s take your item with it’s tags:
"material_tags": "light_source crafted iron"`
I’m sorry, but your item will stay on the ground. Hearthlings can’t store it, because there is no stockpile in vanilla or BS that match these tags. You must add the word “stockpile_decoration”, and it will be stored along with the other light sources and decorations.
Hope this will help. English is not my native language, sorry if my explication is not clear enough.