Illusions refer to deceptive or misleading perceptions or beliefs that deviate from reality. They involve a discrepancy between how something appears and how it actually is. Illusions can occur in various domains, including vision, cognition, and emotions. Visual illusions, such as the famous Müller-Lyer or Ponzo illusions, trick our eyes into perceiving objects differently than they truly are. Cognitive illusions, like the confirmation bias or the availability heuristic, influence our thoughts and decision-making. Emotional illusions involve misperceiving or misinterpreting our own emotions or those of others. Despite their often temporary nature, illusions can profoundly impact our understanding and interactions with the world.