Nice article from the knowledge graph community...
One of my favorite books is "Learning how to learn" it's an older book, published in the 1970s, and one of the techniques it outlined for learning is drawing up a 'Concept Map'.
A Concept Map is exactly what it sounds like, a map of concepts within a specific discipline, and it's the most effective learning tool I've come across for studying very abstract topics like Game Theory.
Actually, I've been quite confused by the term 'Knowledge Graph', is that something that's meant to be machine readable or it's more meant to be read by humans?
They're meant for humans. The short form is that they're yet-another-wiki. :)
Generously, any graph which is directly accessed and analyzed by end-users is a knowledge graph. You could imagine a spectrum from pure applications which happen to use a graph as a back-end, acting as a super-power for advanced application features; all the way to knowledge graphs where applications are just access tools for exploring, consuming, and analyzing the data.
Application == functionality first
Knowledge graph == data/information first
Or maybe, the graph is the application.
Bringing it all the way back to your concept maps, a knowledge graph could be a really big concept map.
"Learning how to learn" is a great book title! Adding it to my stack :)