How does one add textures to weapons?

I see that there is a place to add a symbol and color to an item/weapon but how do you reference that item to a texture in a graphics tileset?

You should add some code to \gfx{TILESET_NAME}\tile_config.json like this:

          "id": "broadsword",
          "fg": 2490,
          "bg": 621,
          "rotates": false

So what does “fg” and “bg” stand for or what do they represent?

first guess, Foreground / background