One exact product reference is a bag of QUIKRETE Concrete Mix labeled 80 lb. That gives a tangible example for “what weighs 80 pounds”; it does not mean every concrete bag or every building-material package weighs the same. QUIKRETE lists its concrete mix in 80-pound bags.
For a quick comparison, 80 lb is the same total weight as two 40 lb loads. In other units, it is 1,280 ounces or approximately 36.3 kilograms. Those conversions describe weight; the shape and volume of an 80-pound object depend on its material and packaging.