Longhorn Cheese is not a type of cheese, but rather an American term used to indicate the size of a block of cheese.
It is a long cylinder about 1 1/2 feet (45 cm) long, and 8 inches (20 cm) wide, weighing about 13 pounds (6 kg.)
To make Longhorn Cheese, at the time of forming the cheese it is pressed into a cylinder-shaped mould, then wrapped in plastic to age. Even if the cheese is to be cut for sale, it’s still usually let age as a whole first.
A Moon is a round slice, cut horizontally through the cheese. The thickness and therefore weight of a “moon” will vary.
The cheese is usually sold in half-moon chunks, which is a half of a moon.
The actual cheese is usually Colby or mild cheddar, but it can even be Monterey Jack. It will always be a firm cheese, though.