Semantics ... is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs, and symbols, and what they stand for, their denotata. 
Questions tagged semantics deal with the meaning of language and signs. Often these are concerned with differences from varing options or the implicated meaning of an artefact.
Terms like semantic markup or semantic web refer to the meaningful nature of how information on the web is presented from source code.
 Source: http://en.wikipedia.org/wiki/Semantics, 2012/01/03