The exact population of monkeys in the world is not known, but there are more than 260 different types of monkeys on the planet. There are two different categories of monkeys: New World and Old World.
All New World monkeys are native to the Americas and have prehensile tails. Most New World monkeys also have round nostrils that are set far apart on their face.
Old World monkeys are native to Africa and Asia and do not have prehensile tails. Old World monkeys also have small pouches in their mouths where they can store food. Their nostrils are curved and close together.