Pragmatics refers to the study of language and the ways context influences meaning. For example, when your partner asks you, “Please take out the garbage,” you might say, “I’ll get to it.” The partner has no doubt heard you use that phrase before and knows what you really mean: “I don’t want to do it.” The garbage will just sit there until your partner gets tired of smelling and tripping over it and finally takes care of it. To contrast, if your supervisor work says, “Please write this memo and cc me on it,” you might say exactly the same thing, “I’ll get to it,” but in this context you actually plan to do it as soon as you finish the task you are currently involved with, and your supervisor knows that because you have said this before and followed through promptly.
Context has a lot to do with the ways human interpret language. In the two instances, context made a difference, even though the words are exactly the same. Humans are linguistic agents, and knowing what to say involves knowing how your utterance will be interpreted in a particular context by your audience.
For additional resources on pragmatics, please see the videos below by Steven Pinker and David Crystal.