What kind of Visualization is this?
Welcome to the site!

I think it is called as Flow Visualization. I remember seeing something similar when I was running a Campaign using Google Analytics. That graph is used for showing the Click-Path Analysis, Visit Flow, Navigation Flow etc. You can go through this link-1, link-2 for better understanding.

The outcome of this graph was to see which path was mostly used and where can we find some room to improve it the ones which are not used mostly, finding the root cause and provide best experience to the users.