Marsupials are a group of mammals known for their unique reproductive system. Unlike most mammals, female marsupials give birth to relatively undeveloped young, which then continue to grow in a pouch on the mother's belly. This pouch provides a safe environment for the young to develop and nurse until they are ready to venture out. Common examples of marsupials include kangaroos, koalas, and opossums. They are primarily found in Australia and New Guinea, although some species, like the opossum, are also present in the Americas. Marsupials play important roles in their ecosystems, often serving as herbivores or predators.