How language interacts with the world, what philosophers call reference, has interested many philosophers of language over the years.
John Stuart Mill believed in a type of direct reference theory, whereby the meaning of an expression lies in what it points out in the world. He identified two components to consider for most terms of a language: denotation (the literal meaning of a word or term) and connotation (the subjective cultural and/or emotional coloration attached to a word or term). According to Mill, proper names (such as of people of places) have only a denotation and no connotation, and that a sentence which refers to a mythical creature, for example, has no meaning (and is neither true nor false) because it has no referent in the real world.
Gottlob Frege was an advocate of a mediated reference theory, which posits that words refer to something in the external world, but insists that there is more to the meaning of a name than simply the object to which it refers. Frege divided the semantic content of every expression (including sentences) into two components: Sinn (usually translated as "sense") and Bedeutung ("meaning", "denotation" or "reference"). The sense of a sentence is the abstract, universal and objective thought that it expresses, but also the mode of presentation of the object that it refers to. The reference is the object or objects in the real world that words pick out, and represents a truth-value (the True or the False). Senses determine reference, and names that refer to the same object can have different senses.
Bertrand Russell, like Frege, was also a Descriptivist of sorts, in that he held that the meanings (or semantic contents) of names are identical to the descriptions associated with them by speakers and a contextually appropriate description can be substituted for the name. But he held that the only directly referential expressions are what he called "logically proper names" such as "I", "now", "here", and other indexicals (terms which symbolically point to or indicate some state of affairs). He described proper names of people or places as abbreviated definite descriptions (the name standing in for a more detailed description of who or what the person or place really is), and considered them not to be meaningful on their own and not directly referential.
Saul Kripke (1940 - ) has argued against Descriptivism on the grounds that names are rigid designators and refer to the same individual in every possible world in which that individual exists.