What does this hitch rating mean?

Whats more that is the maximum for the Receiver, If you use a drop hitch adapter to rasie or lower it, that lowers the ratings, And then there is the towing capacity of the vehicle which may be lower than that of the hitch, the tow rating of the vehicle is either it's rated towing ability or the difference between the actual gross weight of the vehicle and the Combined Gross Vehicle Weight Rating or CGVWR.. in my case 4,000 pounds.

and another thing is that those numbers are the ratings for the hitch receiver ONLY, not necessarily what your vehicle's ratings are.
that same receiver is put on a variety of GM vehicles, all with different towing/hitch capacity ratings.

i have a '07 Avalanche, same GM900 chassis as your Yukon, with the 5.3 and 3.73 rear end and my towing capacity is 7200lbs., much less than what the receiver is rated for.

It means what it says. And it is not a hitch, it is a hitch receiver. You need to install a hitch into the square hole of the receiver.

The hitch receiver is designed for a maximum load of 5000 pounds if carrying the tongue weight of the trailer (not to exceed 500 pounds) or it can accept a 10,000 pound load when a weight distributing hitch is installed and used (tongue load not to exceed 1000 pounds. The latter would assume that the weight distributing hitch you install is also rated for at least 10,000 pounds.

Bottom line is the most important: "Tow vehicle maximum trailer rating may be less." You'll find those numbers in the vehicle owner's manual.

OK, that is what I thought but I was not sure.
Now to look into a WD hitch with sway control and a braking unit.
I am going to try to PU a used 18-24' TT shortly.

The lower rating is simply the dead weight of the trailer without a weight distributing hitch. The higher rate is when using a WD hitch.