What is "Heuristics for understanding" meant here? [closed]

This research paper talks about a term called Heuristic for Understanding Gaming (HUG) but it doesn't say what it actually means by the term. It provides no definition. It only says what the advantages are.

The paper also gives the following diagram.

So, my question is: What does "Heuristics for Understanding" mean here?

Is it a diagram? Is it a flow-chart? Is it a process? Or, something else?

The heuristic is a set of concepts for teachers to understand how the games students play are organized—how they work. The diagram summarizes the heuristic—rules of thumb for the teachers. The idea is that games are structured but allow considerable choice, and in playing them, students acquire knowledge about how complicated structures are put together. The student knowledge of games can be used by the teacher to teach, by analogy, other subjects.

That seems to be what the article is trying to say, whether or not you agree with it.