Let me bleep the shiznat quickly, broadly. Thank you.
from the Greek word semeion meaning "sign" (also meaning 'tomb', 'war-cry', 'flag', 'birthmark', 'symptom', 'omen' -- one of the sorts of words that make Ancient Greek such a 'difficult' languange)
Modern semiotics is one of those cases of simultaneous discovery. In America the founder of Pragmatism, Charles Peirce (1839-1914) wrote on what he called the "semiotic", which in his words is the relationship by which "something stands to somebody for something in some respects or capacity" (Pierce was one of those people who tried to make English a less difficult language). Semiosis, the process of something standing to somebody for something in some respects or capacity, Peirce says, happens among three 'somethings'. These are Object, Sign, and Interpretant. Respectively the 'something' (Object), for which stands in some respcts or capacity 'something' (Sign), for 'somebody' to interpret (which interpretation, not which person is the Interpretant). Got that.
Now, Ferdinand de Saussure (1857-1913) was a Swiss lecturer. He is the inventor of Structural Linguistics. He was the sort of fellow who thought the difficulties of language should be studied. This is what Saussure believed. Language is a collection of signs. A sign is formed signifier/signified pair. The signifier is some perceivable phenonmenon (a voice saying, "cat," for instance) that trigger a signified idea in a listner (for instance, the thought 'I'm hungry for Chinese food'.) The relation between the signifier and signified is arbitrary, you see. Saussure mostly worked in Linguistics, but he realized that signs were present in most human activity. So he placed his linguistics in the broader field of 'Semiology' a discipline he invented but never developed except through linguistics.
The two traditions caught on eventually, under the name of 'Semiotics'. Sometime in the development of Postmodern mentation, after the time of post-structuralism, Semiotics became the latest thing. By the late 1980's quote leading semiotiologists unquote were being interviewed on the Today show, asked about what message celebrities' clothes communicate. Semiotics and deconstruction are fun parlor games. Enjoy. (see irony)