Ann: Sales Contract with Trafigura for Wiluna Gold Concentrate, page-5

This sounds like good news, but I'm not sure I fully understand the implications.
The one part of the process of 1. find gold, 2. dig it up and 3. sell gold which would seem easy is the selling gold part, but here BLK is selling Gold Concentrates rather than pure Gold - so how do we laymen interpret the volume and price?
In this agreement is Trafigura essentially milling / refining? Another way to frame this question is What's in it for them and what's in it for BLK? Can anyone explain how these offtakes work and how the economic benefits are typically shared b/w the 2 parties? Thanks in advance!