Semiotics, or semiotic theory, is a study of how signs and symbols make meaning. This plays a huge role in a variety of areas, including linguistics, art, literature, cinema, politics, and religion.
There are two key figures in the history of semiotics that you should know: Charles Sanders Peirce and Roland Barthes.
Roland Barthes was a French literary critic who extended early semiotic theory to mass media and popular culture. He's considered to be the founder of contemporary semiotics.
Charles Sanders Peirce was an American philosopher and developer of the formal theory of semiotics, and he developed a precise system for describing signs that included terms like symbol, icon, and index.
A sign is something that stands for something other than itself. In other words, it is a representation.
EXAMPLEA stop sign tells you to stop, and a caution sign tells you to be careful. However, neither one shows the actual action of stopping or being cautious.
Ads, such as the one below, can be signs as well.
This image doesn't mean "headlamp," and it doesn't mean "go turn the light on." It stands for something other than itself, so it's advertising a product or communicating that you should buy the product.
A symbol is a sign which has no logical connection to what it signifies. The viewer has to learn the connection between the sign and its meaning.
Look at the logo of the Google Chrome web browser below.
The viewer has to learn that this logo is associated with Chrome as a brand or product, and that it's tied to a service or application— in this case, the browser. It is up to the viewer to learn that connection.
EXAMPLEA flag may symbolize a country or nation, but it does not depict the country or the nation; it's just an abstract symbol. An outsider has to learn the connection to the country from the symbol.
Index is a sign that can be understood because it's logically linked to or affected by what it stands for. To put it simply, an index has a direct link between the sign and the object.
The sign below shows a curvy road, and it's logically linked to its location— it communicates that there is a curvy road ahead.
An icon is a sign that physically resembles what it signifies. A crosswalk sign, for instance, pretty clearly resembles what it's trying to depict, which is, of course, the crosswalk.
Likewise, this icon of an escalator also very clearly resembles what it signifies.
Sometimes an image can be described by more than one of these terms, such as this sign with symbols of the highways and exits.
You could also think of a wedding ring as both a sign and symbol. It’s a sign that the wearer is married, and also a symbol for anything that person chooses to associate it with, such as love.
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR MARIO E. HERNANDEZ