The definition might be a bit confusing, so let's look at some examples to clarify the role of pragmatics in our language. This first example is one that you probably use in your own life every day. Say you are in line at a store to pay for your purchases. The cashier asks, 'How are you today?' Do you immediately go into an in-depth account of your health issues, varying mood, relationship status, and everything else going on in your life? Of course not! Usually, you respond with something similar to, 'Fine, how are you?' with the same expectation that the cashier will not go into full detail of how she truly is. This interaction perfectly shows pragmatics at work. It is understood that this question does not really ask you to explain everything going on in your life. The implication relies on the context and situation. It is good manners to ask strangers how they are, but it is not intended for a detailed response.
Many times you can see pragmatics working when there is an ambiguous meaning - vague or unclear, idea or sentence. As always, the situation will make the ambiguous wording clear. For example, imagine you are at the airport, and you have already checked in your luggage. Then you approach the escalator and see a sign that reads, 'Luggage must be carried on the escalator.' Does this mean that you must return to the counter and get your luggage back so you can carry it on the escalator? Of course not! The understood meaning is that if you have luggage, it should be carried and not rolled on the escalator. You can use the situation to determine the true meaning.