This infographic explains why the brain finds it easier to read information presented in this way. Every day, we're exposed to more information than ever before and visuals help our brain process everything.
This 2009 "subway map" of the Internet is based on Tokyo's subway system. This design company (like a few others, I think) does one of these every year. It's a articular genre of a thing called an "infographic" that you see everywhere.