Yeah after this post I sought a couple youtube videos explaining it. It's starting to make a bit more sense now. But the lightbulb hasn't gone off just yet. Appreciate the link.

Thank you! That's helpful. I got the examples in that Wikipedia section to run using the `--null-input` flag:

  $ jq --null-input '[1, 2] | add'
  3

I wish I had seen this earlier. My mental model was close but not quite there to the point where I needed to think too hard about how to solve problems.

This is much more intuitive now.