Simians are a group of primates that include monkeys, apes, and humans. They are characterized by their flexible limbs, large brains, and social behaviors. Simians are divided into two main categories: New World monkeys, found in the Americas, and Old World monkeys and apes, found in Africa and Asia. These animals typically live in trees and have adaptations for climbing, such as prehensile tails in some species. Simians are known for their complex social structures and communication skills, which can include vocalizations, facial expressions, and body language.