Dogs are mammals, usually to be kept as pets, or work on farms or for the police. Some dogs are trained to be rescue dogs and join teams such as mountain rescue.
Dogs have been bred by humans from ancestral wolves. They were the first animals to live with humans. There was a lot of different types among wolves in the Late Pleistocene.
Today, some dogs are used as pets, and others are used to help humans do their work. They are popular pets because they are usually playful, friendly, loyal, and listen to humans. Thirty million dogs in the United States have been registered as pets. Dogs eat both meat and vegetables, which are often mixed together and sold in stores as dog food. Dogs often have jobs including police dogs, army dogs, assistance dogs, fire dogs, messenger dogs, hunting dogs, herding dogs, or rescue dogs. A baby dog is called a pup or puppy.
Dogs are sometimes known as "human's best friend" because they are kept as pets, are usually loyal, and like being around humans.