Ideas and key words are connected. The lines connecting the words visualize the connection that we make in our minds.
This information could be written down, but it might not be as easily read:
"There are three types of butter. There can be tub butter, margarine (which isn't actually butter), and stick butter. Country Fresh is stick butter. I Can't Believe it's Not Butter isn't really butter, but margarine. It also comes in a tub."