Hitch rating is the rating of the hardware that makes up the hitch, normally 5,000 or 10,000 pounds
Max towing capacity of the vehicle is MAX combined vehicle gross weight MINUS the gross vehicle weight of the tow vehicle.
Your actuall max towing limit is the smaller of the two.
NOTE that if you use a drop/rise hitch adapter the hitch rating is greatly reduced. (read that I did and tore the hitch right off the RV. had to have the brackets where it attaches to the frame re-built the rebuilderds,, As I recall Simpson and Son's serice in Indiana off I think 71, Rebilt them... and then some. )