A zoo is a facility where animals are kept in enclosures for public viewing and education. Zoos often feature a variety of species, including mammals, birds, reptiles, and amphibians. They aim to provide a safe environment for animals while promoting conservation and awareness about wildlife. Many zoos also participate in breeding programs to help endangered species. They often offer educational programs and activities for visitors, teaching them about animal behavior, habitats, and the importance of protecting wildlife. Some well-known zoos include the San Diego Zoo and the Smithsonian National Zoo.