A simile or symbol. A represention or picture of a sacred Christian personage, itself regarded as sacred, especially in the tradition of the Eastern Churches. Icons are images and ideas converted into three dimensions.
Icons are the key to the unspoken attitudes and assumptions of a culture.
Concepts end up as creeds and icons. Every icon, even a pop icon like the Campbell's soup can, bears some trace of the sacred, some suggestion that the reality it presents is natural, transcends culture or mere human agency, is in in some fashion magical. All sacred things must have their place. Being in their place is what makes them sacred. If taken out of their place, even in thought, the entire order of the universe would be destroyed.