is an optical phenomenon
which often occurs naturally. It is produced by the refraction
of light when it passes into a layer of warm air lying close to a heated ground surface, known as a temperature inversion
In deserts, mirages may give the appearance of a lake or other large body of water in the distance; this is actually an image of the sky being refracted back up from the warm air lying over the sand. On tarmacked roads, mirages give the impression of puddles of water in the distance.
Mirage is also the name of fighter aircraft of Dassault Aviation.