Semiotics

Semiotics is the study of signs, signification and symbols as elements of communicative behaviour. A sign can be called a signifier after the Swiss linguist Fernald de Saussure who defined language as a system linking arbitrary symbols or words.
Signs can be found anywhere: above doors, in toilets, on the roads, walls etc...
each sign (or symbol) as its own meaning.

This is a Fire Exit sign. it can be found in every building, usually above the doors or a wall near the nearest exit. Like all signs (or most of them) they have pictures so if a person doesn't understand the language the sign is in then they look at the picture which can be understood (or interpreted) by anyone in the world