A marsupial is a type of mammal that is characterized by giving birth to relatively undeveloped young, which typically continue to grow in a pouch on the mother's belly. This unique reproductive strategy allows the young to receive protection and nourishment while they develop further. Common examples of marsupials include kangaroos, koalas, and opossums. Marsupials are primarily found in Australia and New Guinea, although some species, like the opossum, are native to the Americas. They belong to the infraclass Metatheria and are distinct from placental mammals, which carry their young in the womb for a longer period before birth.