I've been staring at it for several minutes and still can't figure it out. It's presumably about customer flow between brands over time. I think each chord represents some net customer change between two companies and that the color indicates the winner. But the text says Apple lost customers to Samsung and their shared chord is Apple's color.
More mysterious, how should the chord thickness be interpreted? The thickness varies at each end. In other chord diagrams I've seen the thickness is the same at both ends, so maybe this is a variation from the norm.
For example, there is a 1%-wide chord in Nokia that goes to an 8%-wide chord in Samsung. What does that mean? My best guess is that there are two different scales at play, a before and an after since I think this chart is representing change over some period of time. But it's still hard to make sense of it.