Nature is split into many different kinds of living creatures on the Earth. There are also many different ways to classify and define these creatures. One way is the food chain--what a creature eats and also what eats it. Carnivores eat other animals, and a primary carnivore is a type of carnivore.
The food chain represents the transfer of energies in nature needed to survive. The food chain is defined by trophic levels or links of the chain. The chain starts with what are called "producers" of energy, such as plants. The plants are then consumed by a plant-eating animal or a herbivore, representing the second trophic level. Herbivores are then consumed by carnivores, or meat-eating animals, constituting the third trophic level and third link in the chain.
There are other classifications that further define animals inside their respective trophic levels. For example, at the third trophic level carnivores are introduced, but not all carnivores are the same. A primary carnivore, like a cat, represents a carnivore that will only eat herbivores, or plant eaters, such as a mouse. But there are other carnivores.
Primary carnivores must be cautious because of the next trophic level. Representing the next link in the chain are secondary carnivores, or carnivores that will feed on primary carnivores. An examples is a lion eating a boar.
Few species of animals are specifically of one kind of carnivore or another. Think of a bear. In nature it might often be found eating certain kinds of fish that survive off of vegetation in the water, but the bear would also eat other carnivores, like a wolf. A cheetah might eat a giraffe, a herbivore, making the cheetah a primary carnivore in that situation, but the same cheetah might then also eat a jackal, another primary carnviore, making the cheetah a secondary carnivore in this instance.
Although a list of primary carnivores is difficult to determine because the classification of primary and secondary carnivores is relatively fluid, a primary carnivore can be generally identified by its prey. Animals a primary carnivore might eat include plant-eating creatures such as cattle, lambs, giraffes, horses, buffalo, and most birds. By extension, it can be determined that a wolf would almost always be a primary carnviore, since it eats mostly animals like these in the wild, but it could still fulfill the role of a secondary carnivore if it ever preyed on a dog or a cat.