Pragmatics is concerned with the relation of utterances to the contexts in which they are uttered, including the identity of the speaker and hearer, their interests and intentions, the state of their knowledge, their physical surroundings, the business in hand, and so on. Whatever the literal meaning of a sentence might be, it is frequently the case that it acquires additional meaning, and sometimes a wholly different meaning, by virtue of the context in which it is produced. To take a simple example, the sentence ``I love you madly'' has a quite obvious literal meaning, but its full meaning on a given occasion will further depend on exactly who the referents of `I' and `you' are. When the reply comes back, ``And I love you, too, darling,'' the identities of the `I' and `you' will have switched around. Such expressions whose referents change from one occasion of speech to another are called deictic expressions.
Some other deictic expressions are `today', `here', `last month', and so on, whose interpretations depend on the time and the place at which the speaker is talking. Another kind of example of a sentence accruing meaning in addition to its literal meaning might be ``Please check your change before you leave,'' seen in a shop. Its full meaning can only be understood by reference to commonsense knowledge about possible mistakes in counting coins, about standards of honesty, and so on.