The 1396# payload is usually the most important number as you run out of that pretty early on. That is how much you can put in (people, stuff in the bed) and on (trailer tongue weight) the truck. Since that # was derived as the truck was being driven off the factory line you might want to hit a scale to see what it really is. Every floor mat, aftermarket mod and piece of dirt stuck in the tire tread subtracts from that.
A quick example of what you could tow: Take a 5,000# trailer of some type. Typically, 10-15% of that weight goes on the truck (so takes away from your payload). So, you're now down to 800ish# of people and gear you can put in the truck.
The other towing number is what the truck can pull (this is often just called "max towing". IIRC, most 1500s are 7-10K depending on engine and rear gears. So, if your truck was rated at 10,000# it could only pull that with very little else in the truck since as much as 1500# of that 10K would go on the truck as payload.
Great job coming here to learn BEFORE buying something. #1 rule is don't listen to RV salesmen. As far as they're concerned any truck can tow anything. They just never finish the sentence with, "off the lot."