Roland Barthes, a french philosopher is mostly known for his contribution to semiotics. His work Elements of Semiotics can be accessed at http://www.marxists.org/reference/subject/philosophy/works/fr/barthes.htm
Semiotics is the study of signs. It can be interpreted by the "signifier", the sensory clue, or the "signified", the concept. This picture shows an example how how two legos, the signifier, and be interpreted or represented as a plane, the signified.