What is a rhetorics function

Rhetoric is the art of discourse, an art that aims to improve the capability of writers or speakers to inform, most likely to persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the European tradition. Its best known definition comes from Aristotle, who considers it a counterpart of both logic and politics, and calls it "the faculty of observing in any given case the available means of persuasion."