The two groups of monkeys live in different places: the "New World Monkeys" in South America and the "Old World Monkeys" live mainly in Africa and Asia. New World Monkeys are often smaller than Old World Monkeys. Monkeys have long arms and legs to help them swing from trees. Some monkeys' tails can wrap tightly around branches, almost like a "fifth limb". This type of tail is 'prehensile'.