I'm just guessing here but I think this machine sucks up the cut grass and blows it into the cart.
And I just washed my car.
The cart fills up the truck.
I think this guy rakes and fluffs the grass before it is sucked up. I kept trying to get a good photo of the rakes and kept missing.
But the last time the tractor passed my, he lifted the rakes like a peacock his tail. Goodbye till next time. Click to enlarge and see the rakes.