Mirages are light diffusion as a result of heat. The most well-known ones are in the desert.
There is also heat haze. You see this on roads and other places.
There are different types of mirages and technical explanations. The details are beyond me. You are on your own.
We are in the midst of a heat wave in the US. They say it will break on Saturday. Uh, huh. I’ll believe it when I see it.

All of the pictures are from Wikimedia Commons.

Two pictures of heat haze.

Heat haze from jet engines  by, Mean as custard.

633px-Swiss_F-5E_at_Fairford Mean as custard WCHeat haze on a road  by, Brocken Inaglory.

640px-Hot_road_mirage Bocken Inaglory WCGreat Salt Lake in the state of Utah  by, jay galvin.

640px-Great_Salt_Lake_Utah_USA3 jay galvin WCThe last three pictures are by, Brocken Inaglory.

621px-Superior_mirage_of_Point_Reyes_from_SF_ Brocken Inaglory WC640px-Desertmirage Lake mirage Bocken Inaglory WC595px-Complex_superior_mirage_of_a_boat Brocken Inaglory WC