A figure of speech is a word or phrase used in a non-literal way to emphasize a point, be rhetorical, or speak more vividly. Imagery is a figure of speech that creates an image of what is being talked about by engaging all five senses: sight, smell, sound, touch, and taste.
Adjectives are a big part of imagery so the reader or listener can envision the topic. Other figures of speech include metaphors (where one thing is compared to another thing without using the words "like" or "as"), similies (where two things are compared using the words "like" and "as"), and hyperbole (extreme exaggeration).