Cats are obligate carnivores, and in a feral state, they would eat prey that’s high in protein and low in fat and carbohydrates. A cat’s typical prey contains enough moisture to facilitate normal digestion and organ function.
They don’t necessarily need wet food to be healthy, as long as there is enough water in their diets. The quality and content of dry food varies between brands so it’s important to make sure you feed them high quality dry food.