Great question, the hotspots are a very powerful insight. I like them for giving me simple interpretable "rules" about my data.
The x/y axis don't carry any specific meaning. The main part of the visualization is just to highlight different kinds of rules and rules that are similar to each other should be closer to each other. (The graph uses multidimensional scaling to map all the rules in two dimensions).
For more, take a quick peak at the documentation within the app during the trial: