What are rhetorical devices? & What is the difference between that and a rhetorical question?

Rhetoric is the art of persuasion, whether through writing or through speech.

Therefore, rhetorical devices are techniques that are intended to help an author or a speaker be effective in persuading his or her audience.  These devices can be used to emphasize major points, to help organize one's presentation, or to give one's speech or written argument more style.

There are many rhetorical devices.  In fact, the link below lists sixty rhetorical devices.  A rhetorical question is one of those rhetorical devices.

Other rhetorical devices include such things as analogies, alliteration, hyperbole (exaggerating so as to help make a point) and its opposite, understatement.