Semiotics means the study of signs.
It is a theory developed by Swiss professor of linguistics Ferdinand de Saussure (1857-1913). He defined language as a system of representation and argued that meaning is created inside language in the relations of difference between its parts.
Also known as semiology, it is a study of signs and their use, designed to understand systematic regularities from which meaning is derived.
A sign is made up of the matched pair of the signifier and the signified.
The signifier is the phonological or orthographic sound or appearance of a word that can be used to describe or identify something.
The signified is the meaning of a word or expression, the way in which a word or expression or a situation can be interpreted.
For example, a word 'tree' is NOT an actual tree, it only describes, SIGNIFIES the physical object which is the SIGNIFIED.
A signifier without signified has no meaning and signified changes with person and context. The relationship between these two is arbitrary, defined by custom (which is why words describing the same thing sound different in different languages).
A signifier without signified is noise. A signified without a signifier is impossible.
The signifier creates the signified in terms of the meaning it triggers for us.
This theory has very strong links to film and film language is often analyzed through the opposition of the signifier and signified.
Also, in some paradoxical way, semiotics relate to the theory of deconstruction as well. While the deconstruction is attempting to undermine all arbitrary meaning of text, the text itself - formed of language - is arbitrary by nature, because the language is a system or arbitrary signs.
Information quoted from:
http://changingminds.org/explanations/critical_theory/concepts/signifier_signified.htm
