From Wikipedia, the free encyclopedia. This article is about animals kept for companionship. For the use of pet as a verb, see Petting. For other uses of the acronym PET and PETS, see PET (disambiguation) and PETS (disambiguation). A cat and dog, two popular pets. A pet or companion animal is an animal kept primarily for a person's company or protection, as opposed to working animals, sport animals, livestock, and laboratory animals, which are kept primarily for performance, agricultural value, or research.