A retriever is a type of gun dog that retrieves game for a hunter. Generally gun dogs are divided into three major classifications: retrievers, flushing spaniels, and pointing breeds. Retrievers were bred primarily to retrieve birds or other prey and return them to the hunter without damage; retrievers are distinguished in that nonslip retrieval is their primary function. As a result, retriever breeds are bred for soft mouths and a great willingness to please, learn, and obey. A soft mouth refers to the willingness of the dog to carry game in its mouth without biting into it. "Hard mouth" is a serious fault in a hunting dog and is very difficult to correct. A hard-mouthed dog renders game unpresentable or at worst inedible.

Gun dogs or bird dogs are types of hunting dogs developed to assist hunters in finding and retrieving game, typically various fowls that are shot down on the flight. The term hunting dog is broad and includes all breeds and skills of hunting canines, but "gun dogs" refers to canines that are trained to work alongside a loud firearm while hunting or retrieving game. Gun dogs are divided into three main categories: pointers and retrievers, setters and spaniels, and water dogs.