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. The retriever's willingness to please, patient nature and trainability have made breeds such as the Labrador retriever and Golden retriever popular as a disability assistance dog. The outstanding reputation of the retriever has landed both the Labrador and the Golden retriever among the top 10 best dogs for children and families across the world.