A mirage is an optical illusion that occurs when layers of air at different temperatures bend light rays. This bending creates the appearance of water or a reflective surface, often seen on hot roads or deserts. The effect happens because warm air near the ground is less dense than the cooler air above it, causing light to refract. Mirages are most commonly observed in places like deserts or highways on sunny days. They can trick the brain into thinking there is something real, like a pool of water, when in fact, it is just a visual distortion caused by the atmosphere.