Butterflies are insects that go through complete metamorphosis with four distinct life stages - egg, larva, pupa, and adult. They start as eggs laid on leaves by adult butterflies, hatch into caterpillars or larvae that eat voraciously, then form a hardened shell called a chrysalis or pupa where they undergo transformation, emerging as winged butterflies that feed on nectar from flowers. Butterflies play an important role as pollinators in many ecosystems.