How do desert mirages form?

A desert mirage is an optical illusion caused by layers of air at different temperatures. Close to the ground, very hot air is less dense than cooler air above it, so light bends as it passes through the layers. This can make the sky appear as if it is reflecting off the road or sand, creating the look of water in the distance. In some cases, this is called an inferior mirage, which is common on hot roads and desert flats. The effect is not a real pool of water, but a refraction of light in the atmosphere.