Exposition is a literary term that refers to the part of a story that sets the stage for the drama to follow: it introduces the theme, setting, characters, and circumstances at the story’s beginnings. To understand what exposition is, look at how the writer sets the scene for the story and the characters within it
I sharpened my skills under the mentorship of my coach. You need a noun to complete this sentence, and mentorship is the only noun here - the rest of the words are adjectives.