Note: communication is defined as the transfer of information not priorly held by the receiving party. Communication requires transferring content, but the transferring of content does not imply communication.
Content is achieved in a communications medium through the mapping of symbols to semantics. This is not an a priori mapping, much as most of us (English-speakers) would like to feel that the word "tree" directly identifies with the concept "tree", and that the symbol "2" somehow is the quantity "2". The study of this mapping between symbols and semantics is semiotics.
Semiotics has application in a broader context than the level of words and phrases. It also encompasses the mapping between names and identities. Name, in this case, could be a proper name, a nickname, a "handle", an e-mail address, an identification token signed by a third party, etc. See portions of .