Pragmatics is the study of inferred meaning. It is the social force words can take on - beyond their basic semantic value - when used in certain contexts.
Pragmatics needs a consideration of how social context helps create and shape meaning.
It is a vital part of any A-level textual analysis as it is so very revealing of important linguistic aspects. If you ignore the pragmatic force of language in your analyses, you will lose many marks.
Semantics is sometimes said to be the study of sentence meaning; pragmatics to be the study of utterance meaning. This seems confusing - but think of sentence meaning as being that which a dictionary can reveal, whereas utterance meaning requires knowledge of the social context of the whole communication - of the people involved, their social or professional relationship and of other situational aspects pertaining to the time and place in which the words were used.
Pragmatics considers the 'force' language gathers when used in a particular social context.
An example will make this clearer. If you think about the phrase, 'Give him one!', the meaning this contains will very much depend upon the social situation in which it is used. It is the noun 'one' that, in certain social situations, will carry different levels of force: it is a pragmatically loaded word, where its precise meaning can only be inferred by the context of the language use.
Pragmatic meanings can be inferred in this way because, owing to the context of the language use, we are able to 'read into' a word the extra meaning - the utterance's pragmatic force - conferred on it by the way it is used within a particular social situation.
Pragmatics can allow language to be used in interesting and social ways: knowing that your listener or reader shares certain knowledge with you allows your conversation to be more personal, lively or less extended. It also allows you to use words and give them inferred elements such as power aspects, because your listener is aware of your social standing, for example. Similarly, language can act in ideological ways to reinforce a society's values - again, pragmatically. At another level, language users can rely on pragmatics to help them cut down on the number of words needed to make meaning clear - and hence contributes to a more lively style.
Here are a few examples that require more than a semantic analysis to reveal the intended meaning of the text's words and phrases, but where the pragmatic meaning is perfectly clear:
'BABY SALE - GOING CHEAP' (poster seen in shop window - but no babies are for sale).
'Quick! Fire!' (and you know you must run).
'Pass the salt' (and you know it's not an order).
'Are you going into town?' (and you know it's a request for the person to come with you).
'He's got a knife!' (and you don't ask how sharp it is)
'I promise to be good.' (and you don't expect a repeat of the bad deed).
'The present King of England is bald.' (said on TV, yet you can work out what is meant even though we have a queen).
'Another pint...?' (and you know you've already had one).
'I said, 'Now!'' (and you know when).
'I put him forward for the honour.' (and you know who gets it).
'Gosh - it's cold in here!' (and someone shuts the door or window).
An important area of pragmatics is in the study of language and power. The implicit understanding of a power relationship between, say, two speakers, is often indicated by the meanings implied by the language used. This meaning can be very context dependent.