This came with a used reefer 170. So left side is where overflow goes with skimmer, and top right is where return pump goes. What are the other chambers for?
Well if you removed the middle panel on the bottom, you could have a handy space for a refugium. Other than that, looks like they might be used to hold media bags like carbon, purigen, etc.
You sir have a Pro Clear Aquatic Freedom 4-in-1 Sump that middle chamber gives you the option to slide a cartridge type media holder thats sold separately. To the right of that it can be used as a refugium or chamber to house bio media etc.