It's not just topics and subtopics, but associations. They are more powerful, more useful and follow one's own natural set of organizing things.
Taking an example from one of my own mind map - I'm just showing one branch;
................................ Adventure *
................................ /
.Enlightenment - Feeling - Freedom - Direction
......................... \
......................... Restriction - Cleaning
*(insert picture of a RPG Paladin here)
Sorry for bad formatting, the forum software erases my spaces.
There are other branches to enlightenment, but I dont show them here.
Feeling is a part of enlightenment, a result as well as a cause. I had the feeling I didn't have to let my mind go just one track just because I went to work every day. I had an enlightened feeling.
I had the feeling of freedom from a greater choice of options than before. I could look the day from a different angle. I could choose my own restrictions, or make them go away.
I had the restriction of inefficient workplace, and I realized I would have a flowing thought, feeling of freedom in there too, if I cleaned it up.
I would use freedom to take direction somewhere. Understanding my capability to think differently despite boring work, I could use my possibility now.
Exercising freedom would also take me to adventure, of which some RPG games are an image, whereas my adventure can be best realized by acting out my goals.
This organization provided a better understanding for me than a categorical approach.