This theory was to know how this element of persuasion works and how it can be effectively utilized. It is developed from the thought how the language works for people. Rhetoric is often considered as an art, which studies how the things that we said or wrote made changes in the person who reads or hears it.
Thus it studies the effectiveness of language. The rhetoric was an important aspect in ancient western education, especially for the effective oratorical persuasion in fields of politics law. This theory is developed by Aristotle which three elements are needed for an effective communication are speaker, speech, and the listener. Also, there are five canons, Inventio (Invention),Dispositio (Arrangement),Elocutio (Style),Memoria (Memory),Actio (Delivery).
Example of this is when, you ask your mother to buy you something, like you’re persuading her to buy and see what is her reaction if she will buy you by your tone of persuasion. Rhetoric cannot be meaningful without understanding the classical rhetorical theory and to know about classical rhetorical theory we need to know about rhetoric.
Communication Theory 