An imperative sentence is a sentence that always addresses the second person (whether plural or singular) so the subject is implied most of the time (it is not directly stated) and is used to give a command, an instruction, a piece of advice, or to make a request. Here are some examples (Imperative sentences underlined):
<em>Please, </em><u><em>stand up.</em></u><em> </em>(A request)
<u><em>Do not look at me like that!</em></u> (An order)
<em>Please, l</em><u><em>isten to what I say</em></u><em>, </em><u><em>don't be so grumpy</em></u><em>, it will not take anywhere. </em>(Advice)